frontier-squid storageClassName is hard coded to "nfs-provisioner"

[rptaylor]

https://github.com/slateci/slate-catalog/blob/master/stable/osg-frontier-squid/osg-frontier-squid/templates/pvc.yaml#L17

Each cluster may have different CSI provisioners so the storageClassName should be a configurable variable.
In fact, usually it shouldn't need to be set because the cluster's default storageClass should be sufficient. I think a PVC should only need to specify a storageClass if there are multiple types of storage available and it has a strong opinion on which type of storage it wants, so having storageClassName absent (unless defined by the user) may be a suitable default.

Note that the DefaultStorageClass admission controller is enabled by default.

Moreover, to support the use of statically provisioned volumes, it would be good for the helm chart to also support setting volumeName, with storageClassName: "" as described here:
https://kubernetes.io/docs/concepts/storage/persistent-volumes/#reserving-a-persistentvolume
NB storageClassName: "" is different from not having a storageClassName.

[LincolnBryant]

Hi @rptaylor

I think this is a good idea. We'll tackle this shortly! Thanks for the links.

[rptaylor]

@LincolnBryant Okay great. I may be able to make some MRs for straightforward fixes if you want.