Bug description

PVC Creation fails for default storage classes

How to reproduce

Steps to reproduce the behavior:

1. Create a Capsule Tenant Object, with the storage options in the spec. So that tenant can only list storage classes which has label "capsule.clastix.io/tenant-usable"
   ` storageOptions:
   matchExpressions:
   • key: capsule.clastix.io/tenant-usable
     operator: Exists
     `
2. Add the label "capsule.clastix.io/tenant-usable" to all storage classes in the cluster, including the default storage class
3. Create a StatefulSet and define volumeClaimtemplates. But do not put any storage class name in the spec. Let the default storage class be automatically injected to PVC in annotation (volume.beta.kubernetes.io/storage-class) by kubernetes.
4. Describe the stateful set. PVC creation fails with the error
   Warning FailedCreate 2m29s (x177 over 6h57m) statefulset-controller create Pod test-20 in StatefulSet test failed error: failed to create PVC file-test-20: admission webhook "pvc.capsule.clastix.io" denied the request: A valid Storage Class must be used: matching the label selector defined in the Tenant

Expected behavior

PVC creation should be successful, because if we don't specify storage class name in volumeClaimtemplates, kubernetes picks up the default storageclass and set it in annotation (volume.beta.kubernetes.io/storage-class) in PVC, but since capsule checks that pvc must have the storageClassName in the spec it fails. We should also add a check for the annotation (volume.beta.kubernetes.io/storage-class) with the valid storage class name, and if its present then allow the request to create pvc.
Sample code
https://github.com/projectcapsule/capsule/blob/main/pkg/webhook/pvc/validating.go#L48-L56