feat(cluster-handler): integrate resolver and enforce v1alpha1 compliance

This commit refactors the MultigresCluster controller to fully integrate the
new granular resolver logic and ensure strict compliance with the v1alpha1 API.

Changes:
- Integrated `resolver` package to handle the 4-level override chain for
  GlobalTopo, MultiAdmin, Cells, and Shards directly in the reconciler.
- Added in-memory execution of `PopulateClusterDefaults` at the start of
  reconciliation. This guarantees the "System Catalog" (postgres/default/shard-0)
  is injected even if the mutating webhook is disabled or fails.
- Updated child resource creation (Cells, TableGroups) to use the new nested
  `Images` struct, ensuring `ImagePullPolicy` and `ImagePullSecrets` are
  correctly propagated.
- Updated integration tests to respect strict v1alpha1 validation rules
  (Database must be "postgres", TableGroup must be "default").

Author: fernando-villalba

config/crd/bases/multigres.com_cells.yaml

@@ -80,6 +80,44 @@ spec:
                 - implementation
                 - rootPath
                 type: object
+              images:
+                description: Images defines the container images used in this cell.
+                properties:
+                  imagePullPolicy:
+                    description: ImagePullPolicy overrides the default image pull
+                      policy.
+                    enum:
+                    - Always
+                    - Never
+                    - IfNotPresent
+                    type: string
+                  imagePullSecrets:
+                    description: ImagePullSecrets is a list of references to secrets
+                      in the same namespace.
+                    items:
+                      description: |-
+                        LocalObjectReference contains enough information to let you locate the
+                        referenced object inside the same namespace.
+                      properties:
+                        name:
+                          default: ""
+                          description: |-
+                            Name of the referent.
+                            This field is effectively required, but due to backwards compatibility is
+                            allowed to be empty. Instances of this type with an empty value here are
+                            almost certainly wrong.
+                            More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
+                          type: string
+                      type: object
+                      x-kubernetes-map-type: atomic
+                    type: array
+                  multigateway:
+                    description: MultiGateway is the image used for the gateway.
+                    maxLength: 512
+                    type: string
+                required:
+                - multigateway
+                type: object
               multigateway:
                 description: MultiGateway fully resolved config.
                 properties:
@@ -1085,11 +1123,6 @@ spec:
                         type: object
                     type: object
                 type: object
-              multigatewayImage:
-                description: MultiGatewayImage is the image used for the gateway in
-                  this cell.
-                maxLength: 512
-                type: string
               name:
                 description: Name is the logical name of the cell.
                 maxLength: 63
@@ -1246,8 +1279,8 @@ spec:
                 type: string
             required:
             - globalTopoServer
+            - images
             - multigateway
-            - multigatewayImage
             - name
             type: object
             x-kubernetes-validations:

config/crd/bases/multigres.com_shards.yaml

@@ -77,6 +77,34 @@ spec:
                 description: Images defines the container images to be used by this
                   shard (defined globally at MultigresCluster).
                 properties:
+                  imagePullPolicy:
+                    description: ImagePullPolicy overrides the default image pull
+                      policy.
+                    enum:
+                    - Always
+                    - Never
+                    - IfNotPresent
+                    type: string
+                  imagePullSecrets:
+                    description: ImagePullSecrets is a list of references to secrets
+                      in the same namespace.
+                    items:
+                      description: |-
+                        LocalObjectReference contains enough information to let you locate the
+                        referenced object inside the same namespace.
+                      properties:
+                        name:
+                          default: ""
+                          description: |-
+                            Name of the referent.
+                            This field is effectively required, but due to backwards compatibility is
+                            allowed to be empty. Instances of this type with an empty value here are
+                            almost certainly wrong.
+                            More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
+                          type: string
+                      type: object
+                      x-kubernetes-map-type: atomic
+                    type: array
                   multiorch:
                     description: MultiOrch is the image for the shard orchestrator.
                     maxLength: 512

config/crd/bases/multigres.com_tablegroups.yaml

@@ -80,6 +80,34 @@ spec:
                 description: Images defines the container images used for child shards
                   - defined globally in MultigresCluster.
                 properties:
+                  imagePullPolicy:
+                    description: ImagePullPolicy overrides the default image pull
+                      policy.
+                    enum:
+                    - Always
+                    - Never
+                    - IfNotPresent
+                    type: string
+                  imagePullSecrets:
+                    description: ImagePullSecrets is a list of references to secrets
+                      in the same namespace.
+                    items:
+                      description: |-
+                        LocalObjectReference contains enough information to let you locate the
+                        referenced object inside the same namespace.
+                      properties:
+                        name:
+                          default: ""
+                          description: |-
+                            Name of the referent.
+                            This field is effectively required, but due to backwards compatibility is
+                            allowed to be empty. Instances of this type with an empty value here are
+                            almost certainly wrong.
+                            More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/names/#names
+                          type: string
+                      type: object
+                      x-kubernetes-map-type: atomic
+                    type: array
                   multiorch:
                     description: MultiOrch is the image for the shard orchestrator.
                     maxLength: 512