feat(deployment)!: move extraVolumes and extraContainerVolumeMounts into the deployment dict

Both values are Deployment-scoped: `extraVolumes` is rendered into `spec.template.spec.volumes` and
`extraContainerVolumeMounts` only into the volumeMounts of the Gitea container. The `extra*` prefix said
nothing about that scope and left them sitting at the top level, far away from the pod- and container-scoped
settings that already live under `deployment` and `deployment.gitea`.

They therefore become `deployment.volumes` and `deployment.gitea.volumeMounts`, which makes the target
resource and container obvious from the values path alone and continues the consolidation started with
`deployment.gitea.env`, `deployment.gitea.image`, `deployment.gitea.resources` and the security contexts.

`extraInitVolumeMounts` stays where it is for now, because it targets the init containers rather than the
Gitea container. The deprecated `extraVolumeMounts` fallback is kept intact and now points at
`deployment.gitea.volumeMounts` in its documentation.

Both removed keys are covered by the deprecation check, because silently ignoring them would drop mounted
TLS certificates, custom themes or client certs and leave Gitea running with a broken or unexpected
configuration.

BREAKING CHANGE: `extraVolumes` and `extraContainerVolumeMounts` no longer exist. Use `deployment.volumes`
and `deployment.gitea.volumeMounts` instead. Installations that still set the old keys will fail to render
unless `checkDeprecation` is set to `false`.

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

unittests/helm/deployment/deprecations.yaml

@@ -46,6 +46,23 @@ tests:
     asserts:
       - failedTemplate:
           errorMessage: "`dnsConfig` does no longer exist. Please refer to the changelog and configure `deployment.dnsConfig` instead."
+  - it: fails when the removed `extraContainerVolumeMounts` value is set
+    set:
+      extraContainerVolumeMounts:
+        - name: postgres-ssl-vol
+          mountPath: /pg-ssl
+    asserts:
+      - failedTemplate:
+          errorMessage: "`extraContainerVolumeMounts` does no longer exist. Please refer to the changelog and configure `deployment.gitea.volumeMounts` instead."
+  - it: fails when the removed `extraVolumes` value is set
+    set:
+      extraVolumes:
+        - name: postgres-ssl-vol
+          secret:
+            secretName: gitea-postgres-ssl
+    asserts:
+      - failedTemplate:
+          errorMessage: "`extraVolumes` does no longer exist. Please refer to the changelog and configure `deployment.volumes` instead."
   - it: fails when the removed `nodeSelector` value is set
     set:
       nodeSelector:
@@ -130,6 +147,13 @@ tests:
       dnsConfig:
         nameservers:
           - 192.0.2.1
+      extraContainerVolumeMounts:
+        - name: postgres-ssl-vol
+          mountPath: /pg-ssl
+      extraVolumes:
+        - name: postgres-ssl-vol
+          secret:
+            secretName: gitea-postgres-ssl
       nodeSelector:
         foo: bar
       podSecurityContext: