Add volumeClaimTemplates label selector in zeebe statefulSet

[kristeey]

Which problem does the PR fix?

This PR add possibility to use pre-provisioned PVs for zeebe, by doing the following:

1. Add possibility to disable use of default storageClass in the zeebe statefulSet.
2. Enable use of PVC label selector in zeebe statefulSet in order to bind the claim to the desired PV.

What's in this PR?

1. .Values.zeebe.pvcStorageClassName is now checked if equal to "-" (following the standard in the bitnami helm charts)". If so: provide an empty string to the StorageClassName in order to prevent the kubernetes API from using the default storageClass (practically disabling storageClass usage). In earlier versions og this helm chart, whenever setting .Values.zeebe.pvcStorageClassName to "" explicitly, helm interpret this as nil and hence the default storage class is used (if any).
2. .Values.zeebe.pvcSelector, when provided, will provide the possibility to bind PVCs and PVs based on labels. https://kubernetes.io/docs/concepts/storage/persistent-volumes/#selector

Example:

zeebe:
  ...
  pvcStorageClassName: "-"
  pvcSelector:
    matchLabels:
      pv-name: camunda-zeebe-0
    matchExpressions:
      - { key: sku, operator: In, values: [standard, premium] }

Checklist

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[aabouzaid]

No need to make special handling here, using null as a value should have the same effect.

[kristeey]

It was added to follow bitnami standard. But if you want it removed I can change it

[kristeey]

We need some handling here else the default storage class is used, which is not the desired outcome in cases where one wants to use pre provisioned PVs, hence not use storage classes.

[kristeey]

https://github.com/bitnami/charts/blob/main/bitnami/common/templates/_storage.tpl