feat: 迁移 Database Instance 领域基线

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
+}