[kube-prometheus-stack] introduce PVC claim retention field in prometheus operator

[Woojciech]

What this PR does / why we need it

This PR exposes persistentVolumeClaimRetentionPolicy field of Prometheus / PrometheusAgent, a CRD resource from Prometheus operator. PersistentVolumeClaimRetentionPolicy is a feature introduced for StatefulSets (by default in K8s 1.27.0+), this feature lets us decide whether the StatefulSet should delete or retain it's corresponding PVC's it is deleted or scaled. It is particularly useful in environments where stale volumes can grow in amount, causing additional costs or clutter in general. The CRD field itself was added to Prometheus operator around October last year, however not yet exposed in kube-prometheus-stack.

Change provided in this PR is based on the work already present in the prometheus chart , please see the special notes section.

Special notes for your reviewer

This PR is based on the previous work which was made in the prometheus chart, as per links provided below. I wanted to add this exact feature into the chart and I found that it was already done in the linked prometheus operator chart.

Please let me know if relying on the previous implementation has any legal implications (licensing etc.) - if I should for example add authors of mentioned changes as co-authors or provide credits for their work in any other way.

• helm-charts/charts/prometheus/templates/sts.yaml

  Line 17 in c43f4b2

  {{- if semverCompare ">= 1.27.x" (include "prometheus.kubeVersion" .) }}

• helm-charts/charts/prometheus/values.yaml

  Line 588 in c43f4b2

  pvcDeleteOnStsScale: false

Checklist

• DCO signed
• Chart Version bumped
• Title of the PR starts with chart name (e.g. [prometheus-couchdb-exporter])

[Woojciech]

fixed trailing spaces, hopefully everything will be well formatted this time :)

[Woojciech]

Hi @jkroepke can I please ask you for re-approval, as I fixed all the required checks?