feat: 迁移 Database Instance 领域基线

internal/database/domain/instance/credential_reference.go

@@ -0,0 +1,67 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+import (
+	"errors"
+	"regexp"
+)
+
+// CredentialReferenceValues contains effective field mappings, not secret data.
+// The application supplies defaults and fixes the namespace to the controller's.
+// Namespace and provider-specific paths are deliberately not selectable here.
+type CredentialReferenceValues struct {
+	Name        string
+	UsernameKey string
+	PasswordKey string
+}
+
+// CredentialReference is an immutable reference to a management Secret.
+// Its zero value is invalid; aggregate construction must Validate incoming values.
+type CredentialReference struct {
+	values CredentialReferenceValues
+}
+
+// Instance and Secret names share the DNS subdomain syntax and 253-character limit.
+var dnsSubdomainName = regexp.MustCompile(`^[a-z0-9]([-a-z0-9]*[a-z0-9])?(\.[a-z0-9]([-a-z0-9]*[a-z0-9])?)*$`)
+
+func NewCredentialReference(values CredentialReferenceValues) (CredentialReference, error) {
+	reference := CredentialReference{values: values}
+	if err := reference.Validate(); err != nil {
+		return CredentialReference{}, err
+	}
+	return reference, nil
+}
+
+// Values returns a copy of the reference, never secret contents.
+func (r CredentialReference) Values() CredentialReferenceValues { return r.values }
+
+// Validate enforces reference invariants without accessing Kubernetes or OpenBao.
+// Checking that the referenced Secret contains nonempty credentials is an application
+// responsibility. Errors omit input values and no implicit defaults are applied.
+func (r CredentialReference) Validate() error {
+	if len(r.values.Name) > 253 || !dnsSubdomainName.MatchString(r.values.Name) {
+		return errors.New("management Secret name must be a valid DNS subdomain of at most 253 characters")
+	}
+	if r.values.UsernameKey == "" {
+		return errors.New("management Secret username field is required")
+	}
+	if r.values.PasswordKey == "" {
+		return errors.New("management Secret password field is required")
+	}
+	return nil
+}

internal/database/domain/instance/credential_reference_test.go

@@ -0,0 +1,119 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"strings"
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+func validCredentialReference() instance.CredentialReferenceValues {
+	return instance.CredentialReferenceValues{
+		Name: "shared-postgresql-admin", UsernameKey: "username", PasswordKey: "password",
+	}
+}
+
+// Acceptance: docs/database/domain-instance.md §2. References carry names, never credentials or IO.
+func TestCredentialReferenceRejectsInvalidValues(t *testing.T) {
+	cases := []struct {
+		name   string
+		change func(*instance.CredentialReferenceValues)
+	}{
+		{"empty name", func(v *instance.CredentialReferenceValues) { v.Name = "" }},
+		{"uppercase", func(v *instance.CredentialReferenceValues) { v.Name = "Admin" }},
+		{"underscore", func(v *instance.CredentialReferenceValues) { v.Name = "pg_admin" }},
+		{"leading hyphen", func(v *instance.CredentialReferenceValues) { v.Name = "-admin" }},
+		{"trailing hyphen", func(v *instance.CredentialReferenceValues) { v.Name = "admin-" }},
+		{"empty label", func(v *instance.CredentialReferenceValues) { v.Name = "pg..admin" }},
+		{"trailing dot", func(v *instance.CredentialReferenceValues) { v.Name = "pg." }},
+		{"namespace or path", func(v *instance.CredentialReferenceValues) { v.Name = "system/admin" }},
+		{"whitespace", func(v *instance.CredentialReferenceValues) { v.Name = " admin" }},
+		{"too long", func(v *instance.CredentialReferenceValues) { v.Name = strings.Repeat("a", 254) }},
+		{"empty username key", func(v *instance.CredentialReferenceValues) { v.UsernameKey = "" }},
+		{"empty password key", func(v *instance.CredentialReferenceValues) { v.PasswordKey = "" }},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			values := validCredentialReference()
+			tc.change(&values)
+			reference, err := instance.NewCredentialReference(values)
+			if err == nil {
+				t.Fatal("invalid credential reference accepted")
+			}
+			if reference != (instance.CredentialReference{}) {
+				t.Fatal("constructor returned a partial reference on failure")
+			}
+		})
+	}
+}
+
+func TestCredentialReferencePreservesExplicitValues(t *testing.T) {
+	for _, name := range []string{"a", "1", "pg.admin-1", strings.Repeat("a", 253)} {
+		values := validCredentialReference()
+		values.Name = name
+		values.UsernameKey = "PG_USER"
+		values.PasswordKey = "pg.password"
+		reference, err := instance.NewCredentialReference(values)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if reference.Values() != values {
+			t.Fatal("constructor changed the explicit field mapping")
+		}
+		if err := reference.Validate(); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestCredentialReferenceIsAnImmutableComparableValue(t *testing.T) {
+	values := validCredentialReference()
+	reference, err := instance.NewCredentialReference(values)
+	if err != nil {
+		t.Fatal(err)
+	}
+	same, err := instance.NewCredentialReference(values)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if reference != same {
+		t.Fatal("identical references must compare equal")
+	}
+	values.Name = "different"
+	snapshot := reference.Values()
+	snapshot.PasswordKey = "different-key"
+	if reference.Values() != validCredentialReference() {
+		t.Fatal("caller mutated reference through a copy")
+	}
+	if err := (instance.CredentialReference{}).Validate(); err == nil {
+		t.Fatal("zero reference must be invalid")
+	}
+}
+
+func TestCredentialReferenceErrorOmitsInput(t *testing.T) {
+	values := validCredentialReference()
+	values.Name = "canary-sensitive/input"
+	_, err := instance.NewCredentialReference(values)
+	if err == nil {
+		t.Fatal("invalid reference accepted")
+	}
+	if strings.Contains(err.Error(), "canary") {
+		t.Fatal("error included input")
+	}
+}

internal/database/domain/instance/endpoint.go

@@ -0,0 +1,89 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+// Package instance contains the pure domain model of a registered PostgreSQL instance.
+// It does not depend on Kubernetes types, database drivers or credential providers.
+package instance
+
+import (
+	"errors"
+	"net/netip"
+	"regexp"
+)
+
+// TLSMode is an explicit transport policy, not a driver-specific default.
+type TLSMode string
+
+const (
+	TLSDisable    TLSMode = "disable"
+	TLSRequire    TLSMode = "require"
+	TLSVerifyCA   TLSMode = "verify-ca"
+	TLSVerifyFull TLSMode = "verify-full"
+)
+
+// EndpointValues carries explicit, effective values across the application boundary.
+// Defaults are supplied by the API/application mapping, never silently by the domain.
+type EndpointValues struct {
+	Host               string
+	HostAddr           string
+	Port               int
+	ManagementDatabase string
+	TLSMode            TLSMode
+}
+
+// Endpoint is an immutable connection target. Equality compares its declared values,
+// not physical server identity. Its zero value is invalid; aggregate construction
+// must Validate incoming endpoints, even if callers bypass NewEndpoint.
+type Endpoint struct {
+	values EndpointValues
+}
+
+var identifier = regexp.MustCompile(`^[a-z][a-z0-9_]{0,62}$`)
+
+func NewEndpoint(values EndpointValues) (Endpoint, error) {
+	endpoint := Endpoint{values: values}
+	if err := endpoint.Validate(); err != nil {
+		return Endpoint{}, err
+	}
+	return endpoint, nil
+}
+
+// Values returns a copy, without exposing mutable state.
+func (e Endpoint) Values() EndpointValues { return e.values }
+
+// Validate checks local invariants only; it does not resolve DNS or perform IO.
+// Errors intentionally omit input values.
+func (e Endpoint) Validate() error {
+	if e.values.Host == "" {
+		return errors.New("endpoint host is required")
+	}
+	address, err := netip.ParseAddr(e.values.HostAddr)
+	if err != nil || address.Zone() != "" {
+		return errors.New("endpoint host address must be an IPv4 or IPv6 address")
+	}
+	if e.values.Port < 1 || e.values.Port > 65535 {
+		return errors.New("endpoint port must be between 1 and 65535")
+	}
+	if !identifier.MatchString(e.values.ManagementDatabase) {
+		return errors.New("endpoint management database must be a valid PostgreSQL identifier")
+	}
+	switch e.values.TLSMode {
+	case TLSDisable, TLSRequire, TLSVerifyCA, TLSVerifyFull:
+		return nil
+	default:
+		return errors.New("endpoint TLS mode must be explicitly supported")
+	}
+}

internal/database/domain/instance/endpoint_test.go

@@ -0,0 +1,118 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"strings"
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+func validEndpoint() instance.EndpointValues {
+	return instance.EndpointValues{
+		Host: "postgres.home.arpa", HostAddr: "192.0.2.10", Port: 5432,
+		ManagementDatabase: "postgres", TLSMode: instance.TLSVerifyFull,
+	}
+}
+
+// Acceptance: docs/database/domain-instance.md §2, explicit values and no implicit TLS downgrade.
+func TestEndpointRejectsInvalidValues(t *testing.T) {
+	cases := []struct {
+		name   string
+		change func(*instance.EndpointValues)
+	}{
+		{"empty host", func(v *instance.EndpointValues) { v.Host = "" }},
+		{"missing address", func(v *instance.EndpointValues) { v.HostAddr = "" }},
+		{"DNS instead of IP", func(v *instance.EndpointValues) { v.HostAddr = "postgres.home.arpa" }},
+		{"invalid IP", func(v *instance.EndpointValues) { v.HostAddr = "192.0.2.999" }},
+		{"address with port", func(v *instance.EndpointValues) { v.HostAddr = "192.0.2.10:5432" }},
+		{"scoped address", func(v *instance.EndpointValues) { v.HostAddr = "fe80::1%eth0" }},
+		{"zero port", func(v *instance.EndpointValues) { v.Port = 0 }},
+		{"negative port", func(v *instance.EndpointValues) { v.Port = -1 }},
+		{"large port", func(v *instance.EndpointValues) { v.Port = 65536 }},
+		{"empty database", func(v *instance.EndpointValues) { v.ManagementDatabase = "" }},
+		{"uppercase database", func(v *instance.EndpointValues) { v.ManagementDatabase = "Postgres" }},
+		{"leading digit", func(v *instance.EndpointValues) { v.ManagementDatabase = "1postgres" }},
+		{"punctuation", func(v *instance.EndpointValues) { v.ManagementDatabase = "post-gres" }},
+		{"NUL", func(v *instance.EndpointValues) { v.ManagementDatabase = "post\x00gres" }},
+		{"long identifier", func(v *instance.EndpointValues) { v.ManagementDatabase = strings.Repeat("a", 64) }},
+		{"missing TLS mode", func(v *instance.EndpointValues) { v.TLSMode = "" }},
+		{"unsupported TLS mode", func(v *instance.EndpointValues) { v.TLSMode = "prefer" }},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			values := validEndpoint()
+			tc.change(&values)
+			endpoint, err := instance.NewEndpoint(values)
+			if err == nil {
+				t.Fatal("invalid endpoint accepted")
+			}
+			if endpoint != (instance.Endpoint{}) {
+				t.Fatal("constructor returned a partial endpoint on failure")
+			}
+		})
+	}
+}
+
+func TestEndpointPreservesValidValues(t *testing.T) {
+	for _, mode := range []instance.TLSMode{
+		instance.TLSDisable, instance.TLSRequire, instance.TLSVerifyCA, instance.TLSVerifyFull,
+	} {
+		for _, address := range []string{"192.0.2.10", "2001:db8::10"} {
+			for _, port := range []int{1, 65535} {
+				values := validEndpoint()
+				values.TLSMode, values.HostAddr, values.Port = mode, address, port
+				values.ManagementDatabase = "a" + strings.Repeat("_", 62)
+				endpoint, err := instance.NewEndpoint(values)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if endpoint.Values() != values {
+					t.Fatal("constructor changed explicit values")
+				}
+				if err := endpoint.Validate(); err != nil {
+					t.Fatal(err)
+				}
+			}
+		}
+	}
+}
+
+func TestEndpointIsAnImmutableComparableValue(t *testing.T) {
+	values := validEndpoint()
+	endpoint, err := instance.NewEndpoint(values)
+	if err != nil {
+		t.Fatal(err)
+	}
+	same, err := instance.NewEndpoint(values)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if endpoint != same {
+		t.Fatal("identical endpoint values must compare equal")
+	}
+	values.Host = "changed.example"
+	snapshot := endpoint.Values()
+	snapshot.Host = values.Host
+	if endpoint.Values().Host == snapshot.Host {
+		t.Fatal("caller mutated endpoint through a copy")
+	}
+	if err := (instance.Endpoint{}).Validate(); err == nil {
+		t.Fatal("zero endpoint must not be valid")
+	}
+}

internal/database/domain/instance/extensions.go

@@ -0,0 +1,84 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+import "slices"
+
+// ExtensionSet is an immutable set of exact names. Zero represents the empty set.
+// It does not impose identifier syntax or claim that a server supports any name.
+type ExtensionSet struct {
+	names []string
+}
+
+func NewExtensionSet(names []string) ExtensionSet {
+	copied := slices.Clone(names)
+	slices.Sort(copied)
+	return ExtensionSet{names: slices.Compact(copied)}
+}
+
+// Names returns a sorted, deduplicated copy.
+func (s ExtensionSet) Names() []string { return slices.Clone(s.names) }
+
+type ExtensionDecision string
+
+const (
+	ExtensionsAccepted         ExtensionDecision = "Accepted"
+	ExtensionsUnsupported      ExtensionDecision = "ExtensionsUnsupported"
+	ExtensionSupportUnobserved ExtensionDecision = "ExtensionSupportUnobserved"
+)
+
+// ExtensionCheck reports support only, not readiness or permission to install.
+// Unsupported is a detached, sorted list and is populated only for known support.
+type ExtensionCheck struct {
+	Decision    ExtensionDecision
+	Unsupported []string
+}
+
+// ExtensionSupport is the extension-list component of an Instance observation.
+// Zero means unobserved, not an observed empty list. Target/revision binding and
+// invalidation belong to the containing Instance observation, not this set value.
+type ExtensionSupport struct {
+	observed  bool
+	available ExtensionSet
+}
+
+// ObserveExtensionSupport records a successfully read list, including an empty one.
+// A failed query must not call this constructor with an empty list: the application
+// must propagate the dependency failure and leave support unobserved.
+func ObserveExtensionSupport(available []string) ExtensionSupport {
+	return ExtensionSupport{observed: true, available: NewExtensionSet(available)}
+}
+
+// Check performs no IO and cannot install or remove extensions.
+func (s ExtensionSupport) Check(requested ExtensionSet) ExtensionCheck {
+	if len(requested.names) == 0 {
+		return ExtensionCheck{Decision: ExtensionsAccepted}
+	}
+	if !s.observed {
+		return ExtensionCheck{Decision: ExtensionSupportUnobserved}
+	}
+	var unsupported []string
+	for _, name := range requested.names {
+		if _, found := slices.BinarySearch(s.available.names, name); !found {
+			unsupported = append(unsupported, name)
+		}
+	}
+	if len(unsupported) != 0 {
+		return ExtensionCheck{Decision: ExtensionsUnsupported, Unsupported: unsupported}
+	}
+	return ExtensionCheck{Decision: ExtensionsAccepted}
+}

internal/database/domain/instance/extensions_test.go

@@ -0,0 +1,107 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"slices"
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+const (
+	testUUID    = "uuid-ossp"
+	testTrigram = "pg_trgm"
+	testVector  = "vector"
+	testChanged = "changed"
+)
+
+// Acceptance: docs/database/domain-instance.md, extension support is based on observations,
+// not a name regexp or an administrator allowlist.
+func TestExtensionSupportDecisions(t *testing.T) {
+	available := instance.ObserveExtensionSupport([]string{testTrigram, testUUID})
+	cases := []struct {
+		name        string
+		support     instance.ExtensionSupport
+		requested   []string
+		want        instance.ExtensionDecision
+		unsupported []string
+	}{
+		{"unobserved", instance.ExtensionSupport{}, []string{testTrigram}, instance.ExtensionSupportUnobserved, nil},
+		{"observed empty", instance.ObserveExtensionSupport(nil), []string{testTrigram}, instance.ExtensionsUnsupported, []string{testTrigram}},
+		{"empty request", instance.ExtensionSupport{}, nil, instance.ExtensionsAccepted, nil},
+		{"supported", available, []string{testUUID, testTrigram, testTrigram}, instance.ExtensionsAccepted, nil},
+		{"unsupported", available, []string{testVector, "hstore", testVector, testTrigram},
+			instance.ExtensionsUnsupported, []string{"hstore", testVector}},
+		{"exact names", available, []string{"PG_TRGM"}, instance.ExtensionsUnsupported, []string{"PG_TRGM"}},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			result := tc.support.Check(instance.NewExtensionSet(tc.requested))
+			if result.Decision != tc.want || !slices.Equal(result.Unsupported, tc.unsupported) {
+				t.Fatalf("Check() = %v, want %v / %v", result, tc.want, tc.unsupported)
+			}
+		})
+	}
+}
+
+func TestExtensionSetCopiesAndCanonicalizesNames(t *testing.T) {
+	input := []string{testUUID, testTrigram, testUUID}
+	set := instance.NewExtensionSet(input)
+	input[0] = testChanged
+	names := set.Names()
+	want := []string{testTrigram, testUUID}
+	if !slices.Equal(names, want) {
+		t.Fatalf("Names() = %v, want %v", names, want)
+	}
+	names[0] = testChanged
+	if !slices.Equal(set.Names(), want) {
+		t.Fatal("returned slice mutated set")
+	}
+	if len((instance.ExtensionSet{}).Names()) != 0 {
+		t.Fatal("zero set must be empty")
+	}
+	// Names are preserved exactly; actual server support, not a local regexp, is decisive.
+	unusual := []string{"Vendor.Extension", testUUID}
+	if result := instance.ObserveExtensionSupport(unusual).Check(instance.NewExtensionSet(unusual)); result.Decision != instance.ExtensionsAccepted {
+		t.Fatal("imposed a local name restriction")
+	}
+}
+
+func TestExtensionSupportCopiesObservationAndResults(t *testing.T) {
+	input := []string{testTrigram}
+	support := instance.ObserveExtensionSupport(input)
+	input[0] = testVector
+	requested := instance.NewExtensionSet([]string{testTrigram, testVector})
+	result := support.Check(requested)
+	if !slices.Equal(result.Unsupported, []string{testVector}) {
+		t.Fatal("input mutation changed observation")
+	}
+	result.Unsupported[0] = testChanged
+	again := support.Check(requested)
+	if !slices.Equal(again.Unsupported, []string{testVector}) {
+		t.Fatal("result mutation changed subsequent decision")
+	}
+	// Replacing an observation does not mutate the old value or produce uninstall actions.
+	empty := instance.ObserveExtensionSupport(nil)
+	if empty.Check(requested).Decision != instance.ExtensionsUnsupported {
+		t.Fatal("empty observation ignored")
+	}
+	if support.Check(instance.NewExtensionSet([]string{testTrigram})).Decision != instance.ExtensionsAccepted {
+		t.Fatal("new observation mutated old value")
+	}
+}

internal/database/domain/instance/identity.go

@@ -0,0 +1,73 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+import "errors"
+
+// Identity identifies one registration, not a physical PostgreSQL server.
+// UID is opaque; a recreated resource with the same name has a different identity.
+// Its zero value is invalid and must be rejected when constructing an aggregate.
+type Identity struct {
+	uid  string
+	name string
+}
+
+func NewIdentity(uid, name string) (Identity, error) {
+	identity := Identity{uid: uid, name: name}
+	if err := identity.Validate(); err != nil {
+		return Identity{}, err
+	}
+	return identity, nil
+}
+
+func (i Identity) UID() string  { return i.uid }
+func (i Identity) Name() string { return i.name }
+
+// Validate checks registration values without looking up any external identity.
+func (i Identity) Validate() error {
+	if i.uid == "" {
+		return errors.New("instance UID is required")
+	}
+	if len(i.name) > 253 || !dnsSubdomainName.MatchString(i.name) {
+		return errors.New("instance name must be a valid DNS subdomain of at most 253 characters")
+	}
+	return nil
+}
+
+// Revision is a positive configuration generation, separate from Identity.
+// Zero is invalid for desired configuration; an unobserved status generation of
+// zero must be represented separately when the aggregate is implemented.
+type Revision struct {
+	value int64
+}
+
+func NewRevision(value int64) (Revision, error) {
+	revision := Revision{value: value}
+	if err := revision.Validate(); err != nil {
+		return Revision{}, err
+	}
+	return revision, nil
+}
+
+func (r Revision) Value() int64 { return r.value }
+
+func (r Revision) Validate() error {
+	if r.value <= 0 {
+		return errors.New("instance revision must be positive")
+	}
+	return nil
+}

internal/database/domain/instance/identity_test.go

@@ -0,0 +1,102 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"math"
+	"strings"
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+// Acceptance: docs/database/domain-instance.md §2: registration identity is UID + name,
+// independent of the configuration revision or physical PostgreSQL server.
+func TestIdentityDistinguishesRecreatedInstances(t *testing.T) {
+	first, err := instance.NewIdentity("opaque-uid-1", "shared")
+	if err != nil {
+		t.Fatal(err)
+	}
+	same, err := instance.NewIdentity("opaque-uid-1", "shared")
+	if err != nil {
+		t.Fatal(err)
+	}
+	recreated, err := instance.NewIdentity("opaque-uid-2", "shared")
+	if err != nil {
+		t.Fatal(err)
+	}
+	if first != same || first == recreated {
+		t.Fatal("identity must distinguish same-name registrations by UID")
+	}
+	if first.UID() != "opaque-uid-1" || first.Name() != "shared" {
+		t.Fatal("identity changed declared values")
+	}
+	if err := first.Validate(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestIdentityValidation(t *testing.T) {
+	for _, name := range []string{"", "Shared", "shared_name", "ns/shared", "-shared", "pg..shared", strings.Repeat("a", 254)} {
+		identity, err := instance.NewIdentity("uid", name)
+		if err == nil || identity != (instance.Identity{}) {
+			t.Fatal("invalid name accepted or partial identity returned")
+		}
+	}
+	if _, err := instance.NewIdentity("", "shared"); err == nil {
+		t.Fatal("empty UID accepted")
+	}
+	if err := (instance.Identity{}).Validate(); err == nil {
+		t.Fatal("zero identity accepted")
+	}
+	for _, name := range []string{"a", "1", "pg.shared-1", strings.Repeat("a", 253)} {
+		if _, err := instance.NewIdentity("opaque-not-a-uuid", name); err != nil {
+			t.Fatal(err)
+		}
+	}
+}
+
+func TestRevisionRequiresPositiveValue(t *testing.T) {
+	for _, value := range []int64{math.MinInt64, -1, 0} {
+		revision, err := instance.NewRevision(value)
+		if err == nil || revision != (instance.Revision{}) {
+			t.Fatal("invalid revision accepted or partial value returned")
+		}
+	}
+	for _, value := range []int64{1, 2, math.MaxInt64} {
+		revision, err := instance.NewRevision(value)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if revision.Value() != value {
+			t.Fatal("revision changed declared value")
+		}
+		if err := revision.Validate(); err != nil {
+			t.Fatal(err)
+		}
+		same, err := instance.NewRevision(value)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if revision != same {
+			t.Fatal("identical revisions must compare equal")
+		}
+	}
+	if err := (instance.Revision{}).Validate(); err == nil {
+		t.Fatal("zero revision accepted")
+	}
+}

internal/database/domain/instance/instance.go

@@ -0,0 +1,101 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+import "errors"
+
+// Phase is a workflow checkpoint, never evidence of external resource state.
+type Phase string
+
+const (
+	PhasePending              Phase = "Pending"
+	PhaseValidating           Phase = "Validating"
+	PhaseInitializingRegistry Phase = "InitializingRegistry"
+	PhaseReady                Phase = "Ready"
+	PhaseDeleting             Phase = "Deleting"
+)
+
+type Readiness string
+
+const (
+	Unknown  Readiness = "Unknown"
+	Ready    Readiness = "Ready"
+	NotReady Readiness = "NotReady"
+)
+
+// Snapshot contains persisted observations only, without credentials or live evidence.
+// Failure detail mapping will be added with capability assessment, not intent transitions.
+type Snapshot struct {
+	Phase            Phase
+	ObservedRevision int64
+	Readiness        Readiness
+	ReportedVersion  string
+}
+
+// Instance protects registration state and pure lifecycle transitions.
+// Reconstitution does not establish live capability evidence, even for a Ready snapshot.
+// This initial slice deliberately exposes no operation that authorizes provisioning.
+type Instance struct {
+	target   ObservationTarget
+	snapshot Snapshot
+	deleting bool
+}
+
+func Reconstitute(target ObservationTarget, snapshot Snapshot, deleting bool) (*Instance, error) {
+	if err := target.Validate(); err != nil {
+		return nil, err
+	}
+	switch snapshot.Phase {
+	case PhasePending, PhaseValidating, PhaseInitializingRegistry, PhaseReady, PhaseDeleting:
+	default:
+		snapshot.Phase = PhasePending
+		snapshot.Readiness = Unknown
+	}
+	return &Instance{target: target, snapshot: snapshot, deleting: deleting}, nil
+}
+
+func (i *Instance) Target() ObservationTarget { return i.target }
+
+// Snapshot returns a detached value. Persisting it remains the application's job.
+func (i *Instance) Snapshot() Snapshot { return i.snapshot }
+
+// BeginValidation records intent only; it does not claim a concluded observation.
+func (i *Instance) BeginValidation() error {
+	if err := i.target.Validate(); err != nil {
+		return err
+	}
+	if i.deleting {
+		return errors.New("cannot begin validation after deletion was requested")
+	}
+	i.snapshot.Phase = PhaseValidating
+	i.snapshot.Readiness = Unknown
+	return nil
+}
+
+// BeginDeletion stops the lifecycle from accepting validation. It does not delete
+// resources, inspect Tenant references, close connections or modify finalizers.
+func (i *Instance) BeginDeletion() error {
+	if err := i.target.Validate(); err != nil {
+		return err
+	}
+	if !i.deleting {
+		return errors.New("cannot begin deletion without a deletion request")
+	}
+	i.snapshot.Phase = PhaseDeleting
+	i.snapshot.Readiness = Unknown
+	return nil
+}

internal/database/domain/instance/instance_test.go

@@ -0,0 +1,134 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+func lifecycleInstance(t *testing.T, snapshot instance.Snapshot, deleting bool) *instance.Instance {
+	t.Helper()
+	identity, revision, definition := targetParts(t)
+	target, err := instance.NewObservationTarget(identity, revision, definition)
+	if err != nil {
+		t.Fatal(err)
+	}
+	value, err := instance.Reconstitute(target, snapshot, deleting)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return value
+}
+
+// Acceptance: docs/database/domain-instance.md §3, checkpoint reconstruction and intent-only transitions.
+func TestReconstituteCheckpoints(t *testing.T) {
+	for _, phase := range []instance.Phase{
+		instance.PhasePending, instance.PhaseValidating, instance.PhaseInitializingRegistry,
+		instance.PhaseReady, instance.PhaseDeleting,
+	} {
+		snapshot := instance.Snapshot{Phase: phase, ObservedRevision: 1, Readiness: instance.Ready, ReportedVersion: "17"}
+		value := lifecycleInstance(t, snapshot, false)
+		if value.Snapshot() != snapshot {
+			t.Fatal("known checkpoint was not preserved")
+		}
+		// A snapshot is detached; it is not a setter on the aggregate.
+		copy := value.Snapshot()
+		copy.Phase = instance.PhasePending
+		copy.ReportedVersion = "changed"
+		if value.Snapshot() != snapshot {
+			t.Fatal("snapshot mutation changed aggregate")
+		}
+	}
+	for _, phase := range []instance.Phase{"", "unknown"} {
+		value := lifecycleInstance(t, instance.Snapshot{Phase: phase, Readiness: instance.Ready}, false)
+		if value.Snapshot().Phase != instance.PhasePending || value.Snapshot().Readiness != instance.Unknown {
+			t.Fatal("missing or unknown checkpoint did not restart conservatively")
+		}
+	}
+	if value, err := instance.Reconstitute(instance.ObservationTarget{}, instance.Snapshot{}, false); err == nil || value != nil {
+		t.Fatal("invalid target reconstructed an aggregate")
+	}
+}
+
+func TestBeginValidationPreservesObservedRevision(t *testing.T) {
+	snapshot := instance.Snapshot{
+		Phase: instance.PhaseReady, ObservedRevision: 0, Readiness: instance.Ready, ReportedVersion: "17",
+	}
+	value := lifecycleInstance(t, snapshot, false)
+	target := value.Target()
+	for range 2 {
+		if err := value.BeginValidation(); err != nil {
+			t.Fatal(err)
+		}
+		got := value.Snapshot()
+		if got.Phase != instance.PhaseValidating || got.Readiness != instance.Unknown ||
+			got.ObservedRevision != snapshot.ObservedRevision || got.ReportedVersion != snapshot.ReportedVersion {
+			t.Fatal("recording validation intent claimed a completed observation or erased diagnostic version")
+		}
+	}
+	if value.Target() != target {
+		t.Fatal("lifecycle action mutated identity or configuration")
+	}
+}
+
+func TestDeletionRequiresRequestAndPreventsValidation(t *testing.T) {
+	snapshot := instance.Snapshot{Phase: instance.PhaseReady, Readiness: instance.Ready, ObservedRevision: 1}
+	active := lifecycleInstance(t, snapshot, false)
+	if err := active.BeginDeletion(); err == nil {
+		t.Fatal("deletion without a request accepted")
+	}
+	if active.Snapshot() != snapshot {
+		t.Fatal("rejected deletion mutated state")
+	}
+	for _, phase := range []instance.Phase{
+		instance.PhasePending, instance.PhaseValidating, instance.PhaseInitializingRegistry,
+		instance.PhaseReady, instance.PhaseDeleting,
+	} {
+		snapshot.Phase = phase
+		value := lifecycleInstance(t, snapshot, true)
+		if err := value.BeginValidation(); err == nil {
+			t.Fatal("validation accepted after deletion request")
+		}
+		if value.Snapshot() != snapshot {
+			t.Fatal("rejected validation mutated state")
+		}
+		for range 2 {
+			if err := value.BeginDeletion(); err != nil {
+				t.Fatal(err)
+			}
+			if got := value.Snapshot(); got.Phase != instance.PhaseDeleting || got.Readiness != instance.Unknown ||
+				got.ObservedRevision != snapshot.ObservedRevision {
+				t.Fatal("incorrect deletion checkpoint")
+			}
+		}
+	}
+}
+
+func TestZeroInstanceCannotTransition(t *testing.T) {
+	var value instance.Instance
+	if err := value.BeginValidation(); err == nil {
+		t.Fatal("zero instance started validation")
+	}
+	if err := value.BeginDeletion(); err == nil {
+		t.Fatal("zero instance started deletion")
+	}
+	if value.Snapshot() != (instance.Snapshot{}) {
+		t.Fatal("invalid transition changed zero instance")
+	}
+}

internal/database/domain/instance/observation_target.go

@@ -0,0 +1,81 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance
+
+// Definition is the immutable effective configuration of an Instance.
+// Available extensions are observations, not part of the declared configuration.
+type Definition struct {
+	endpoint        Endpoint
+	adminCredential CredentialReference
+}
+
+func NewDefinition(endpoint Endpoint, adminCredential CredentialReference) (Definition, error) {
+	definition := Definition{endpoint: endpoint, adminCredential: adminCredential}
+	if err := definition.Validate(); err != nil {
+		return Definition{}, err
+	}
+	return definition, nil
+}
+
+func (d Definition) Endpoint() Endpoint                   { return d.endpoint }
+func (d Definition) AdminCredential() CredentialReference { return d.adminCredential }
+
+// Validate rejects invalid zero-value components even when constructors were bypassed.
+func (d Definition) Validate() error {
+	if err := d.endpoint.Validate(); err != nil {
+		return err
+	}
+	return d.adminCredential.Validate()
+}
+
+// ObservationTarget binds facts to a registration and its declared configuration.
+// It does not identify a physical PostgreSQL server or prove observation freshness.
+// Secret content refresh and same-target observation freshness remain application
+// responsibilities; no credentials or Secret contents are carried by this value.
+type ObservationTarget struct {
+	identity   Identity
+	revision   Revision
+	definition Definition
+}
+
+func NewObservationTarget(identity Identity, revision Revision, definition Definition) (ObservationTarget, error) {
+	target := ObservationTarget{identity: identity, revision: revision, definition: definition}
+	if err := target.Validate(); err != nil {
+		return ObservationTarget{}, err
+	}
+	return target, nil
+}
+
+func (t ObservationTarget) Identity() Identity     { return t.identity }
+func (t ObservationTarget) Revision() Revision     { return t.revision }
+func (t ObservationTarget) Definition() Definition { return t.definition }
+
+func (t ObservationTarget) Validate() error {
+	if err := t.identity.Validate(); err != nil {
+		return err
+	}
+	if err := t.revision.Validate(); err != nil {
+		return err
+	}
+	return t.definition.Validate()
+}
+
+// Matches rejects invalid targets before comparing values. Matching is necessary,
+// but not sufficient, for the aggregate to accept a fresh capability observation.
+func (t ObservationTarget) Matches(other ObservationTarget) bool {
+	return t.Validate() == nil && other.Validate() == nil && t == other
+}

internal/database/domain/instance/observation_target_test.go

@@ -0,0 +1,165 @@
+/*
+Copyright 2026.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package instance_test
+
+import (
+	"testing"
+
+	"git.ddupan.top/panxiao81/ayatori/internal/database/domain/instance"
+)
+
+func targetParts(t *testing.T) (instance.Identity, instance.Revision, instance.Definition) {
+	t.Helper()
+	identity, err := instance.NewIdentity("uid-1", "shared")
+	if err != nil {
+		t.Fatal(err)
+	}
+	revision, err := instance.NewRevision(1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	endpoint, err := instance.NewEndpoint(validEndpoint())
+	if err != nil {
+		t.Fatal(err)
+	}
+	credential, err := instance.NewCredentialReference(validCredentialReference())
+	if err != nil {
+		t.Fatal(err)
+	}
+	definition, err := instance.NewDefinition(endpoint, credential)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return identity, revision, definition
+}
+
+func TestDefinitionRejectsInvalidComponents(t *testing.T) {
+	_, _, definition := targetParts(t)
+	cases := []struct {
+		endpoint   instance.Endpoint
+		credential instance.CredentialReference
+	}{
+		{instance.Endpoint{}, definition.AdminCredential()},
+		{definition.Endpoint(), instance.CredentialReference{}},
+	}
+	for _, tc := range cases {
+		value, err := instance.NewDefinition(tc.endpoint, tc.credential)
+		if err == nil || value != (instance.Definition{}) {
+			t.Fatal("invalid component accepted or partial value returned")
+		}
+	}
+	if err := (instance.Definition{}).Validate(); err == nil {
+		t.Fatal("zero definition accepted")
+	}
+}
+
+func TestObservationTargetRejectsInvalidComponents(t *testing.T) {
+	identity, revision, definition := targetParts(t)
+	cases := []struct {
+		identity   instance.Identity
+		revision   instance.Revision
+		definition instance.Definition
+	}{
+		{instance.Identity{}, revision, definition},
+		{identity, instance.Revision{}, definition},
+		{identity, revision, instance.Definition{}},
+	}
+	for _, tc := range cases {
+		value, err := instance.NewObservationTarget(tc.identity, tc.revision, tc.definition)
+		if err == nil || value != (instance.ObservationTarget{}) {
+			t.Fatal("invalid component accepted or partial target returned")
+		}
+	}
+	zero := instance.ObservationTarget{}
+	if err := zero.Validate(); err == nil {
+		t.Fatal("zero target accepted")
+	}
+	if zero.Matches(zero) {
+		t.Fatal("two invalid targets must not authorize observation reuse")
+	}
+}
+
+// Acceptance: docs/database/domain-instance.md §2/§6, observations cannot cross target bindings.
+func TestObservationTargetMatchesOnlySameBinding(t *testing.T) {
+	identity, revision, definition := targetParts(t)
+	original, err := instance.NewObservationTarget(identity, revision, definition)
+	if err != nil {
+		t.Fatal(err)
+	}
+	same, err := instance.NewObservationTarget(identity, revision, definition)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !original.Matches(same) || original.Identity() != identity ||
+		original.Revision() != revision || original.Definition() != definition {
+		t.Fatal("target did not preserve its declared binding")
+	}
+	changedIdentity, err := instance.NewIdentity("uid-2", identity.Name())
+	if err != nil {
+		t.Fatal(err)
+	}
+	changedRevision, err := instance.NewRevision(2)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, parts := range []struct {
+		identity instance.Identity
+		revision instance.Revision
+	}{{changedIdentity, revision}, {identity, changedRevision}} {
+		changed, err := instance.NewObservationTarget(parts.identity, parts.revision, definition)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if original.Matches(changed) || changed.Matches(original) {
+			t.Fatal("different registration or revision matched")
+		}
+	}
+	endpointValues := definition.Endpoint().Values()
+	endpointValues.Host = "other.example"
+	endpoint, err := instance.NewEndpoint(endpointValues)
+	if err != nil {
+		t.Fatal(err)
+	}
+	credentialValues := definition.AdminCredential().Values()
+	credentialValues.PasswordKey = "replacement"
+	credential, err := instance.NewCredentialReference(credentialValues)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, components := range []struct {
+		endpoint   instance.Endpoint
+		credential instance.CredentialReference
+	}{{endpoint, definition.AdminCredential()}, {definition.Endpoint(), credential}} {
+		changedDefinition, err := instance.NewDefinition(components.endpoint, components.credential)
+		if err != nil {
+			t.Fatal(err)
+		}
+		changed, err := instance.NewObservationTarget(identity, revision, changedDefinition)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if original.Matches(changed) {
+			t.Fatal("changed definition matched even with the same revision")
+		}
+	}
+	if original.Matches(instance.ObservationTarget{}) {
+		t.Fatal("valid target matched zero target")
+	}
+	if !original.Matches(same) {
+		t.Fatal("constructing changed targets mutated the original")
+	}
+}