Adds StatefulSet support (#549)

* Adds StatefulSet support

# Conflicts:
#	helm/opengist/templates/pvc.yaml

* Adds statefulset support for replicaCount gt 1

* Improves the setup of multiple replicas in a stateful set

* Adds config wrangling logic to the secret template

* Adds shared PV functionality

* Adds missing pvc-shared template

* Adds stateful set and documentation

---------

Co-authored-by: Guillem Riera <guillem@rieragalm.es>

helm/opengist/templates/pvc-shared.yaml

@@ -0,0 +1,48 @@
+{{- /*
+This template creates a standalone PersistentVolumeClaim for shared persistence mode.
+
+Rendering conditions:
+  - statefulSet.enabled=true
+  - persistence.enabled=true
+  - persistence.mode=shared
+  - persistence.existingClaim is empty/unset
+  - persistence.create.enabled=true
+
+When rendered, this PVC is mounted by ALL replicas in the StatefulSet (typically with ReadWriteMany
+access mode for multi-replica deployments). This avoids per-replica volumeClaimTemplates and enables
+horizontal scaling with a single shared storage backend.
+
+If persistence.existingClaim is set, this template does NOT render; the StatefulSet instead references
+the existing claim name directly.
+*/}}
+{{- if and .Values.statefulSet.enabled .Values.persistence.enabled (eq (default "perReplica" .Values.persistence.mode) "shared") (ne (default "" .Values.persistence.existingClaim) "") | not }}{{- end }}
+{{- if and .Values.statefulSet.enabled .Values.persistence.enabled (eq (default "perReplica" .Values.persistence.mode) "shared") (eq (default "" .Values.persistence.existingClaim) "") .Values.persistence.create.enabled }}
+apiVersion: v1
+kind: PersistentVolumeClaim
+metadata:
+  name: {{ include "opengist.fullname" . }}-{{ default "shared" .Values.persistence.create.nameSuffix }}
+  labels:
+    {{- include "opengist.labels" . | nindent 4 }}
+    {{- with .Values.persistence.create.labels }}
+    {{- toYaml . | nindent 4 }}
+    {{- end }}
+  {{- with .Values.persistence.create.annotations }}
+  annotations:
+    {{- toYaml . | nindent 4 }}
+  {{- end }}
+spec:
+  accessModes:
+    {{- if .Values.persistence.create.accessModes }}
+    {{- toYaml .Values.persistence.create.accessModes | nindent 4 }}
+    {{- else }}
+    - ReadWriteMany
+    {{- end }}
+  resources:
+    requests:
+      storage: {{ default .Values.persistence.size .Values.persistence.create.size }}
+  volumeMode: Filesystem
+  {{- $sc := default .Values.persistence.storageClass .Values.persistence.create.storageClass }}
+  {{- if $sc }}
+  storageClassName: {{ $sc | quote }}
+  {{- end }}
+{{- end }}