fix(helm): configure version for snapshot api

[kmova]

On some managed K8s clusters like OpenShift or GKE that ship with
their own default CSI Drivers, the controllers will end up creating
v1beta1 objects. An issue like the following was noticed when running
cstor charts on GKE 1.19.

 unable to recognize "": no matches for kind "VolumeSnapshotClass" in
 version "snapshot.storage.k8s.io/v1"

This commit uses the helm .Capabilities to check the version available
in the cluster and install the class accordingly. As the .Capabilities
might return false when using with template command, v1 is kept for false
(or default) case.

Manually verified on GKE with and without setting the flag as follows:

kiran_mova_mayadata_io@kmova-dev:charts$ helm install openebs-cstor . -n openebs --create-namespace --set openebsNDM.enabled =false 

NAME: openebs-cstor
LAST DEPLOYED: Fri Jul 16 16:55:45 2021
NAMESPACE: openebs
STATUS: deployed
REVISION: 1
TEST SUITE: None
NOTES:
The OpenEBS cstor has been installed check its status by running:
....

Also, verified that v1 version is generated when running helm template

Signed-off-by: kmova kiran.mova@mayadata.io

[shovanmaity]

We can make use of built in object Capabilities.APIVersions.Has to know if that version is available in the cluster or not. One reference is here - https://github.com/helm/charts/blob/f4f301ae450101b981805bd045451f08c0d74afa/stable/rethinkdb/templates/rethinkdb-cluster-storage-class.yaml#L2-L6

[kmova]

Thanks @shovanmaity - using .Capabilities is very clean. Updated the code.

[shovanmaity]

One more changes requested. Sorry I have not explained it explained properly..
There could be 2 versions present but kind can belong to any one of them so we need to include kind also

apiVersion: {{ if .Capabilities.APIVersions.Has "snapshot.storage.k8s.io/v1beta1/VolumeSnapshotClass" -}}
  snapshot.storage.k8s.io/v1beta1
{{- else -}}
  snapshot.storage.k8s.io/v1
{{- end }}

ref - https://helm.sh/docs/chart_template_guide/builtin_objects

[shovanmaity]

$ kubectl api-versions | grep "snapshot.storage.k8s.io"
snapshot.storage.k8s.io/v1
snapshot.storage.k8s.io/v1beta1

$ kubectl api-resources | grep VolumeSnapshotClass
volumesnapshotclasses                                              snapshot.storage.k8s.io/v1beta1             false        VolumeSnapshotClass

As we are providing only v1 crd according to this code if v1 crd installed it will fail as snapshot.storage.k8s.io/v1 and snapshot.storage.k8s.io/v1beta1 both are available and snapshot.storage.k8s.io/v1/VolumeSnapshotClass is available but snapshot.storage.k8s.io/v1beta1/VolumeSnapshotClass is not available

[kmova]

Above comment is fixed in #362