[friedrichg]

What this PR does:

Adds parquet_converter.statefulSet.enabled, the same switch as ingester.statefulSet.enabled, so that the parquet converter can run as a StatefulSet with a persistent volume per pod.

The converter downloads each block into its data_dir before it converts it, and it wipes <data_dir>/compact before each download, so replicas must not share a volume. As a Deployment it has no volume of its own: the container runs with readOnlyRootFilesystem: true, so the default data_dir (./data) cannot be written unless extraVolumes adds one, and a generic ephemeral volume there is created and deleted with every pod.

With parquet_converter.statefulSet.enabled: true:

• The converter is a StatefulSet (templates/parquet-converter/parquet-converter-statefulset.yaml) and the Deployment is not rendered.
• Each pod gets a Persistent Volume Claim named storage from parquet_converter.persistentVolume (size, storageClass, accessModes, annotations, subPath), or an emptyDir when persistentVolume.enabled is false, mounted at /data. The image's working directory is /, so the default data_dir ./data is on that volume with no config change.
• The claim belongs to the pod's ordinal, so a restart, a rollout or an eviction keeps the same volume.
• persistentVolume.retentionPolicy sets persistentVolumeClaimRetentionPolicy (Kubernetes 1.23 and later), as for the ingester, store-gateway and compactor.
• statefulSet.podManagementPolicy defaults to Parallel, because the converter ring does not need ordered starts. statefulStrategy is the StatefulSet's updateStrategy.

The default stays a Deployment, so nothing changes for existing users.

Which issue(s) this PR fixes:
None.

Testing:

• helm template with the default values (Deployment), with statefulSet.enabled (StatefulSet with a storage claim mounted at /data), with persistentVolume.enabled: false (emptyDir), and with retentionPolicy, storageClass: "-" and subPath set: each renders as expected.
• kubectl apply --dry-run=server of the rendered StatefulSet on kind (Kubernetes v1.35.0): accepted.
• README regenerated with helm-docs v1.11.0.
• The CI install test values do not enable the parquet converter, so CI covers the new template through ct lint only.

Checklist

• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX], [DEPENDENCY]

[SungJin1212]

Should we mount an emptyDir to the Deployment as a default?

[kd7lxl]

Can you rebase this?