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/deployment.yaml

@@ -1,3 +1,4 @@
+{{- if not .Values.statefulSet.enabled }}
 apiVersion: apps/v1
 kind: Deployment
 metadata:
@@ -124,3 +125,5 @@ spec:
       tolerations:
         {{- toYaml . | nindent 8 }}
       {{- end }}
+
+{{- end }}