Feature Request: Add extraObjects support to the cluster Helm chart

# Feature Request: Add `extraObjects` support to the cluster Helm chart ## Problem When deploying a CNPG cluster via the `cluster` Helm chart, related resources like ConfigMaps, NetworkPolicies, PrometheusRules, Secrets/ExternalSecret and so on must be managed outside the Helm release. Either via a wrapper chart, Kustomize overlays, or separate manifests. ## Proposed solution Add an `extraObjects` value (list, default `[]`) rendered as additional manifests, passed through `tpl` for templating support. **`values.yaml`:** ```yaml # -- Extra Kubernetes manifests to deploy alongside the cluster. # Each entry is passed through `tpl`, so Helm templating is supported. extraObjects: [] # - apiVersion: v1 # kind: ConfigMap # metadata: # name: "{{ include \"cluster.fullname\" . }}-grafana-dashboard" # labels: # grafana_dashboard: "1" # data: # cnpg-dashboard.json: |- # { ... } # - | # apiVersion: v1 # kind: Secret # type: Opaque # metadata: # name: cnpg-cluster-secret # data: # { ... } ``` **`templates/extra-manifests.yaml`:** ```yaml {{- /* Normalize extraObjects to a list, easier to loop over */ -}} {{- $extraObjects := .Values.extraObjects | default (list) -}} {{- if kindIs "map" $extraObjects -}} {{- $extraObjects = values $extraObjects -}} {{- end -}} {{- range $extraObjects }} --- {{- if kindIs "map" . }} {{- tpl (toYaml .) $ | nindent 0 }} {{- else if kindIs "string" . }} {{- tpl . $ | nindent 0 }} {{- end }} {{- end }} ``` ## Prior art This is a well-established pattern: **Loki** ([[values.yaml](https://github.com/grafana/loki/blob/main/production/helm/loki/values.yaml)](https://github.com/grafana/loki/blob/main/production/helm/loki/values.yaml)), **Traefik** ([[#595](https://github.com/traefik/traefik-helm-chart/issues/595)](https://github.com/traefik/traefik-helm-chart/issues/595)), **cert-manager** ([[#5900](https://github.com/cert-manager/cert-manager/issues/5900)](https://github.com/cert-manager/cert-manager/issues/5900)), **Bitnami** (`extraDeploy`), **Flux2**, and many others. There's even an open discussion to make this a first-class Helm feature: [[helm/helm#12653](https://github.com/helm/helm/issues/12653)](https://github.com/helm/helm/issues/12653). ## Implementation effort One new template file, one new default value. Non-breaking, minimal change.