fix: address PostgreSQL registry review

internal/postgresql/registry/sql.go

@@ -16,36 +16,6 @@ limitations under the License.
 
 package registry
 
-var bootstrapStatements = []string{
-	`CREATE SCHEMA IF NOT EXISTS postgresql_tenant_operator`,
-	`CREATE TABLE IF NOT EXISTS postgresql_tenant_operator.schema_version (
-    singleton boolean PRIMARY KEY DEFAULT true CHECK (singleton),
-    version integer NOT NULL
-)`,
-	`INSERT INTO postgresql_tenant_operator.schema_version (singleton, version)
-VALUES (true, 1)
-ON CONFLICT (singleton) DO NOTHING`,
-	`CREATE TABLE IF NOT EXISTS postgresql_tenant_operator.tenant_ownership (
-    instance_uid text NOT NULL,
-    tenant_uid text NOT NULL,
-    tenant_namespace text NOT NULL,
-    tenant_name text NOT NULL,
-    database_name text NOT NULL,
-    role_name text NOT NULL,
-    credential_path text NOT NULL,
-    managed boolean NOT NULL DEFAULT true,
-    created_at timestamptz NOT NULL DEFAULT clock_timestamp(),
-    updated_at timestamptz NOT NULL DEFAULT clock_timestamp(),
-    retained_at timestamptz,
-    PRIMARY KEY (instance_uid, tenant_uid),
-    UNIQUE (instance_uid, tenant_namespace, tenant_name),
-    UNIQUE (instance_uid, database_name),
-    UNIQUE (instance_uid, role_name),
-    UNIQUE (credential_path),
-    CHECK (managed OR retained_at IS NOT NULL)
-)`,
-}
-
 const claimStatement = `
 INSERT INTO postgresql_tenant_operator.tenant_ownership (
     instance_uid,
@@ -56,7 +26,19 @@ INSERT INTO postgresql_tenant_operator.tenant_ownership (
     role_name,
     credential_path
 ) VALUES ($1, $2, $3, $4, $5, $6, $7)
-ON CONFLICT DO NOTHING`
+ON CONFLICT DO NOTHING
+RETURNING
+    instance_uid,
+    tenant_uid,
+    tenant_namespace,
+    tenant_name,
+    database_name,
+    role_name,
+    credential_path,
+    managed,
+    created_at,
+    updated_at,
+    retained_at`
 
 const getByTenantUIDStatement = `
 SELECT