Allow configuring additional containers in Helm chart

[imstevenxyz]

The PR introduces the ability to configure additional containers in the controllerplugin and nodeplugin pods.

Why

For our use-case we need to run additional setup alongside cvmfs-csi. The Helm chart currently has no way of creating additional containers in the deployment of the controller plugin or the daemonset of the node plugin.

Example

The additional containers can be configured in the values file as follows:

nodeplugin:
  extraContainers:
    - name: node-sidecar-example
      image: alpine:latest
      ...

controllerplugin:
  extraContainers:
    - name: controller-sidecar-example
      image: alpine:latest
      ...