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.yaml

@@ -1,4 +1,4 @@
-{{- if and .Values.persistence.enabled (not .Values.persistence.existingClaim) }}
+{{- if and .Values.persistence.enabled (not .Values.statefulSet.enabled) (not .Values.persistence.existingClaim) }}
 kind: PersistentVolumeClaim
 apiVersion: v1
 metadata:
@@ -25,4 +25,4 @@ spec:
   resources:
     requests:
       storage: {{ .Values.persistence.size }}
-{{- end }}
+{{- end }}