Clarify that Connect with off-host execution requires a PV and PVC

[SamEdwardes]

helm/charts/rstudio-connect/README.md

Lines 48 to 54 in c48d94f

	* A Kubernetes [PersistentVolume](https://kubernetes.io/docs/concepts/storage/persistent-volumes/) that contains the data directory for Connect.
	* If `sharedStorage.create` is set, a PVC that relies on the default storage class will be created to generate the PersistentVolume.
	Most Kubernetes environments do not have a default storage class that you can use with `ReadWriteMany` access mode out-of-the-box.
	In this case, we recommend you disable `sharedStorage.create` and create your own `PersistentVolume` and `PersistentVolumeClaim`, then
	mount them into the container by specifying the `pod.volumes` and `pod.volumeMounts` parameters, or by specifying your `PersistentVolumeClaim` using `sharedStorage.name` and `sharedStorage.mount`.
	* If you cannot use a `PersistentVolume` to properly mount your data directory, you'll need to mount your data in the container
	by using a regular [Kubernetes Volume](https://kubernetes.io/docs/concepts/storage/volumes), specified in `pod.volumes` and `pod.volumeMounts`.

[kevinchiang]

I think it would be useful to provide an example for the second bullet point. Including which path(s) the volumeMounts need to be mounted

# Configures shared storage for the RStudio Connect pod.
# sharedStorage:
#   create: false
#   mount: false
#   accessModes: ["ReadWriteMany"]
#   volumeName: rstudio-connect-pv

#   # The name of the PVC that will be created for Connect's data directory.
#   # This PVC is also specified by `Launcher.DataDirPVCName` below.
#   name: rstudio-connect-pvc


# Enables building and executing content in isolated Kubernetes pods.
launcher:
  enabled: true
  defaultInitContainer:
    enabled: true
    repository: --private-registry-omitted--/artifactory/api/docker/ghcr-io-docker-remote/rstudio/rstudio-connect-content-init
    tagPrefix: bionic-
  templateValues:
    pod:
      imagePullPolicy: Always
      imagePullSecrets:
        - name: regsecret
      volume:
        - name: rsc-volume
          nfs:
            server: --omitted--
            path: /rstudio_connect
      volumeMounts:
        - mountPath: /opt/rstudio-connect
          name: rsc-volume
        - mountPath: /mnt/rstudio-connect-runtime
          name: rsc-volume

trying to deploy a chart on 0.4.2 results in the following error message:

Error: execution error at (rstudio-connect/templates/NOTES.txt:46:6):

When launcher is enabled, persistent storage must be provided.
This is usually done via a PersistentVolumeClaim (PVC) with `sharedStorage.create=true`, although there are other options.

[SamEdwardes]

An example in the comments would be great. But we should be evident in the README that a PV and PVC are hard requirements. I have seen this need to be clarified for users who have tried to deploy off-host execution without a PV/PVC.

[edavidaja]

Connect now supports using a raw NFS volume:
https://docs.posit.co/connect/admin/appendix/off-host/external-storage/index.html#option-2-using-a-raw-nfs-volume
some additional documentation on storage configurations for Connect is here:
https://docs.posit.co/helm/examples/connect/#storage