feat(common): allow for CNPG UID/GID (#31499)

**Description**


⚒️ Fixes  #27350

**⚙️ Type of change**

- [x] ⚙️ Feature/App addition
- [ ] 🪛 Bugfix
- [ ] ⚠️ Breaking change (fix or feature that would cause existing
functionality to not work as expected)
- [ ] 🔃 Refactor of current code

**🧪 How Has This Been Tested?**
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**📃 Notes:**
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**✔️ Checklist:**

- [ ] ⚖️ My code follows the style guidelines of this project
- [ ] 👀 I have performed a self-review of my own code
- [ ] #️⃣ I have commented my code, particularly in hard-to-understand
areas
- [ ] 📄 I have made corresponding changes to the documentation
- [ ] ⚠️ My changes generate no new warnings
- [ ] 🧪 I have added tests to this description that prove my fix is
effective or that my feature works
- [ ] ⬆️ I increased versions for any altered app according to semantic
versioning
- [ ] I made sure the title starts with `feat(chart-name):`,
`fix(chart-name):` or `chore(chart-name):`

**➕ App addition**

If this PR is an app addition please make sure you have done the
following.

- [ ] 🖼️ I have added an icon in the Chart's root directory called
`icon.png`

---

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---------

Co-authored-by: Stavros Kois <s.kois@outlook.com>

charts/library/common-test/tests/cnpg/cluster_recovery_spec_test.yaml

@@ -40,6 +40,8 @@ tests:
             imageName: ghcr.io/cloudnative-pg/postgresql:16.3
             primaryUpdateStrategy: unsupervised
             primaryUpdateMethod: switchover
+            postgresUID: 26
+            postgresGID: 26
             logLevel: info
             instances: 2
             nodeMaintenanceWindow:

charts/library/common-test/tests/cnpg/cluster_spec_test.yaml

@@ -36,6 +36,77 @@ tests:
             imageName: ghcr.io/cloudnative-pg/postgresql:16.3
             primaryUpdateStrategy: unsupervised
             primaryUpdateMethod: switchover
+            postgresUID: 26
+            postgresGID: 26
+            logLevel: info
+            instances: 2
+            nodeMaintenanceWindow:
+              reusePVC: true
+              inProgress: false
+            resources:
+              limits:
+                cpu: 4000m
+                memory: 8Gi
+              requests:
+                cpu: 10m
+                memory: 50Mi
+            storage:
+              pvcTemplate:
+                accessModes:
+                  - ReadWriteOnce
+                resources:
+                  requests:
+                    storage: 100Gi
+            walStorage:
+              pvcTemplate:
+                accessModes:
+                  - ReadWriteOnce
+                resources:
+                  requests:
+                    storage: 100Gi
+            bootstrap:
+              initdb:
+                secret:
+                  name: test-release-name-common-test-cnpg-my-pg-user
+                database: test-db
+                owner: test-user
+                dataChecksums: true
+  - it: should work with custom UID/GID
+    set:
+      postgres16Image:
+        repository: ghcr.io/cloudnative-pg/postgresql
+        tag: "16.3"
+        pullPolicy: IfNotPresent
+      cnpg:
+        my-pg:
+          enabled: true
+          user: test-user
+          database: test-db
+          password: test-password
+          cluster:
+            postgresUID: 666
+            postgresGID: 666
+    asserts:
+      - documentIndex: &clusterDoc 0
+        isKind:
+          of: Cluster
+      - documentIndex: *clusterDoc
+        isAPIVersion:
+          of: postgresql.cnpg.io/v1
+      - documentIndex: *clusterDoc
+        equal:
+          path: metadata.name
+          value: test-release-name-common-test-cnpg-my-pg
+      - documentIndex: *clusterDoc
+        equal:
+          path: spec
+          value:
+            enableSuperuserAccess: true
+            imageName: ghcr.io/cloudnative-pg/postgresql:16.3
+            postgresUID: 666
+            postgresGID: 666
+            primaryUpdateStrategy: unsupervised
+            primaryUpdateMethod: switchover
             logLevel: info
             instances: 2
             nodeMaintenanceWindow:
@@ -69,7 +140,6 @@ tests:
                 database: test-db
                 owner: test-user
                 dataChecksums: true
-
   - it: should respect changed fallbackDefaults
     set:
       postgres15Image:
@@ -192,6 +262,8 @@ tests:
             imageName: some-image
             primaryUpdateStrategy: supervised
             primaryUpdateMethod: restart
+            postgresUID: 26
+            postgresGID: 26
             logLevel: debug
             instances: 3
             initdb:
@@ -239,6 +311,8 @@ tests:
             imageName: some-image
             primaryUpdateStrategy: supervised
             primaryUpdateMethod: restart
+            postgresUID: 26
+            postgresGID: 26
             logLevel: debug
             instances: 3
             nodeMaintenanceWindow:

charts/library/common/templates/class/cnpg/_cluster.tpl

@@ -177,6 +177,9 @@ metadata:
   {{- end }}
 spec:
   imageName: {{ $imageName }}
+  {{/* This ignores `0` on purpose. */}}
+  postgresUID: {{ $objectData.cluster.postgresUID | default 26 }}
+  postgresGID: {{ $objectData.cluster.postgresGID | default 26 }}
   enableSuperuserAccess: {{ $enableSuperUser }}
   primaryUpdateStrategy: {{ $primaryUpdateStrategy }}
   primaryUpdateMethod: {{ $primaryUpdateMethod }}