Check for Default Storage Class when storageClassName is empty

[manavellamnimble]

@marccampbell @dexhorthy Good morning! I send you the PR to check for a storage class set as default when storageClassName is empty. I can add the parse function to parse the string "true" to bool, but it would also consider other values as "True", "T", "TRUE"...and I think k8s only expect the value true

The default StorageClass has an annotation storageclass.kubernetes.io/is-default-class set to true. Any other value or absence of the annotation is interpreted as false.

Closes #200

src: https://kubernetes.io/docs/tasks/administer-cluster/change-default-storage-class/#changing-the-default-storageclass (item 2)

[codelingo]

LGTM.

[dexhorthy]

Hi @manavellamnimble thanks for the PR! I think I'm in favor of only supporting exactly what Kubernetes supports (or what they document to support) -- if adding an annotation value of (string) T or yes causes the kubectl get storageclass output to change, then we should treat that as valid:

NAME             PROVISIONER               AGE
standard         kubernetes.io/gce-pd      1d
gold (default)   kubernetes.io/gce-pd      1d

But if Kubernetes only parses the "true" string for this then we should only allow that. Does that make sense?

[codelingo]

LGTM.

[manavellamnimble]

@markpundsack @dexhorthy I've added default messages in case storageClassName is empty and no message is provided.

[codelingo]

LGTM.

[markpundsack]

Logic and messaging looks good to me. I haven't validated the code functionality.