csi-snapshot-controller support

[theboringstuff]

Description

For CSI VolumeSnapshot functionality to work, an additional CRDs and snapshot-controller are required:

• https://github.com/kubernetes-csi/external-snapshotter/tree/master

Solution

• Created csi-snapshot-controller chart and plugin based on it. There is no official chart, only community one https://github.com/piraeusdatastore/helm-charts/tree/main/charts/snapshot-controller. However, community chart has issues, so we create our own chart based on it (removed a lot of redundant things).
  • Plugin also allows to deploy additionalResources to deploy VolumeSnapshotClass CR after chart installation.
• Snapshot controller only works with recent versions of openstack-cinder-csi, because old openstack-cinder-csi v1.22 contains a bug. Thus, we now recommend to always install latest openstack-cinder-csi, even on old OpenStacks. This is possible due to special option in cloud.conf as described in documentation
• Updated documentation to describe new csi-snapshot-controller plugin and also changed recommendations about openstack-cinder-csi on old OpenStacks

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• There is no breaking changes, or migration patch is provided
• Integration CI passed
• Unit tests. If Yes list of new/changed tests with brief description
• There is no merge conflicts