feat!: remove the postgresql sub-chart

With `cloudnativePG` in place, the bundled Bitnami `postgresql` sub-chart is the second in-chart way to run a
database, and the worse one. It is a single, non-HA instance without failover, backup or managed major-version
upgrades, and it ships images that Bitnami no longer distributes freely. Keeping it around means maintaining two
code paths for the same job, including the mutual-exclusion assertion between both dependencies and a second set
of DNS, credential and image helpers.

Removing it leaves exactly two supported choices: a CloudNativePG `Cluster` rendered by this chart, or an
external database configured via `gitea.config.database`. Both scale from a single instance to a HA setup -
`cloudnativePG.instances=1` covers the use case the `postgresql` sub-chart served - so nothing is lost besides
the duplication.

BREAKING CHANGE: The `postgresql` sub-chart and all `postgresql.*` values have been removed. There is no
in-place migration path: dump the database of the old `postgresql` release with `pg_dump`, remove the
`postgresql` values, deploy the chart with `cloudnativePG.enabled=true` and restore the dump. Alternatively
point `gitea.config.database` at an externally managed database. Setting `postgresql` now fails the release with
a pointer to the changelog.

Co-authored-by: Copilot <copilot@github.com>

unittests/helm/dependency-checks/customizationIntegrityPostgresql.yaml

@@ -1,102 +0,0 @@
-suite: Test dependency customization integrity of postgresql
-release:
-  name: gitea-unittests
-  namespace: testing
-set:
-  cloudnativePG:
-    enabled: false
-  postgresql:
-    enabled: true
-    global:
-      postgresql:
-        auth:
-          password: gitea-password
-          database: gitea-database
-          username: gitea-username
-        service:
-          ports:
-            postgresql: 1234
-    primary:
-      persistence:
-        size: 1337Mi
-tests:
-  - it: "[postgresql] Apply the database settings"
-    template: charts/postgresql/templates/primary/statefulset.yaml
-    asserts:
-      - documentIndex: 0
-        contains:
-          path: spec.template.spec.containers[0].env
-          content:
-            name: POSTGRES_DATABASE
-            value: "gitea-database"
-      - documentIndex: 0
-        contains:
-          path: spec.template.spec.containers[0].env
-          content:
-            name: POSTGRES_USER
-            value: "gitea-username"
-  - it: "[postgresql] Apply the database password"
-    template: charts/postgresql/templates/secrets.yaml
-    asserts:
-      - documentIndex: 0
-        equal:
-          path: data["password"]
-          value: "Z2l0ZWEtcGFzc3dvcmQ="
-  - it: "[postgresql] Apply primary.persistence.size"
-    template: charts/postgresql/templates/primary/statefulset.yaml
-    asserts:
-      - documentIndex: 0
-        equal:
-          path: spec.volumeClaimTemplates[0].spec.resources.requests.storage
-          value: "1337Mi"
-  - it: "[postgresql] Apply global.postgresql.service.ports.postgresql"
-    template: charts/postgresql/templates/primary/svc.yaml
-    asserts:
-      - documentIndex: 0
-        equal:
-          path: spec.ports[0].port
-          value: 1234
-  - it: "[postgresql] Render the referenced Service"
-    template: charts/postgresql/templates/primary/svc.yaml
-    asserts:
-      - containsDocument:
-          kind: Service
-          apiVersion: v1
-          name: gitea-unittests-postgresql
-          namespace: testing
-  - it: "[gitea] Connect to the postgresql Service"
-    template: templates/secret_inlineConfig.yaml
-    asserts:
-      - documentIndex: 0
-        matchRegex:
-          path: data.database
-          decodeBase64: true
-          pattern: HOST=gitea-unittests-postgresql.testing.svc.cluster.local:1234
-  - it: "[gitea] Connect to the postgresql Service with a custom cluster domain"
-    set:
-      clusterDomain: my-special-cluster.local
-    template: templates/secret_inlineConfig.yaml
-    asserts:
-      - documentIndex: 0
-        matchRegex:
-          path: data.database
-          decodeBase64: true
-          pattern: HOST=gitea-unittests-postgresql.testing.svc.my-special-cluster.local:1234
-  - it: "[gitea] Connect to the configured database"
-    template: templates/secret_inlineConfig.yaml
-    asserts:
-      - documentIndex: 0
-        matchRegex:
-          path: data.database
-          decodeBase64: true
-          pattern: NAME=gitea-database
-      - documentIndex: 0
-        matchRegex:
-          path: data.database
-          decodeBase64: true
-          pattern: USER=gitea-username
-      - documentIndex: 0
-        matchRegex:
-          path: data.database
-          decodeBase64: true
-          pattern: PASSWD=gitea-password

unittests/helm/dependency-checks/majorImageBump.yaml

@@ -3,19 +3,6 @@ release:
   name: gitea-unittests
   namespace: testing
 tests:
-  - it: "[postgresql] Detect major image version upgrades"
-    template: charts/postgresql/templates/primary/statefulset.yaml
-    set:
-      postgresql:
-        enabled: true
-      cloudnativePG:
-        enabled: false
-    asserts:
-      - documentIndex: 0
-        matchRegex:
-          path: spec.template.spec.containers[0].image
-          # IN CASE OF AN INTENTIONAL MAJOR BUMP, ADJUST THIS TEST
-          pattern: bitnamilegacy/postgresql:17.+$
   - it: "[valkey] Detect major image version upgrades"
     template: charts/valkey/templates/deploy_valkey.yaml
     set: