Add Nutanix CSI snapshot controller addon

[xmudrii]

What this PR does / why we need it:

This PR extends the Nutanix CSI driver addon to add the snapshot controller. The rest of the description explains how to test the snapshot controller.

Once the cluster is provisioned, create a VolumeSnapshotClass:

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
  name: vsc
driver: csi.nutanix.com
parameters:
  storageType: NutanixVolumes
  csi.storage.k8s.io/snapshotter-secret-name: ntnx-secret
  csi.storage.k8s.io/snapshotter-secret-namespace: kube-system
deletionPolicy: Delete

After that, create a PVC and a pod that will use it:

---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: csi-pvc-ntnx
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
  storageClassName: ntnx-csi
---
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    ports:
    - containerPort: 80
      protocol: TCP
    volumeMounts:
      - mountPath: /var/lib/www/html
        name: csi-data-ntnx
  volumes:
  - name: csi-data-ntnx
    persistentVolumeClaim:
      claimName: csi-pvc-ntnx
      readOnly: false

Exec to the nginx pod and write some files in the /var/lib/www/html directory. After that, snapshot the volume:

apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: snapshot1
spec:
  volumeSnapshotClassName: vsc
  source:
    persistentVolumeClaimName: csi-pvc-ntnx

Wait for the snapshot to be complete, and then remove the PVC and the pod. Wait a while, and then create a new PVC that uses the snapshot:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: csi-pvc-ntnx-restored
spec:
  storageClassName: ntnx-csi
  dataSource:
    name: snapshot1
    kind: VolumeSnapshot
    apiGroup: snapshot.storage.k8s.io
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 1Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: nginx
spec:
  containers:
  - image: nginx
    imagePullPolicy: IfNotPresent
    name: nginx
    ports:
    - containerPort: 80
      protocol: TCP
    volumeMounts:
      - mountPath: /var/lib/www/html
        name: csi-data-ntnx
  volumes:
  - name: csi-data-ntnx
    persistentVolumeClaim:
      claimName: csi-pvc-ntnx-restored
      readOnly: false

Exec to the pod and check are the files you created earlier present.

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #1726

Does this PR introduce a user-facing change?:

Extend the Nutanix CSI driver addon with the snapshot controller (see the PR description for more details)

/assign @kron4eg

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[embik]

We do not deploy the snapshot controller for other CSI addons (Azure, AWS) as separate addons but embed it into the CSI driver addon, why is this handled differently?

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 2947767199b03d9deff039bd684213566f135348

[xmudrii]

We do not deploy the snapshot controller for other CSI addons (Azure, AWS) as separate addons but embed it into the CSI driver addon, why is this handled differently?

We tend to organize addons in the same way as the vendor. In this concrete case, Nutanix provides the CSI driver and the snapshot controller as two separate Helm charts, therefore we have two addons. This makes maintaining, upgrading, and keeping addons in sync easier. Technically, it doesn't matter much, besides the fact that users will have to enable two addons if they want to use both.

[xmudrii]

/hold
Let's merge those two addons.

[xmudrii]

/hold cancel

[kubermatic-bot]

LGTM label has been added.

Git tree hash: 500d626825ddfe5303e7b2a9a645812ee8b40f46