fix(vd): vdsnapshot without size annotation

[danilrwx]

Description

Handle legacy VirtualDiskSnapshot restores for NFS snapshots that do not have the virtualization.deckhouse.io/vd-original-size annotation.

When a VirtualDisk is restored from such a snapshot and the source StorageClass provisioner is nfs.csi.k8s.io, the controller no longer falls back to VolumeSnapshot.status.restoreSize silently. Instead, it stops provisioning and waits for the user to specify spec.persistentVolumeClaim.size explicitly.

The change adds:

• SnapshotSizeFallback condition on VirtualDisk;
• DataSourceImportFallback warning event;
• tests for NFS and non-NFS provisioners.

Why do we need it, and what problem does it solve?

Legacy NFS snapshots may not contain the original requested VirtualDisk size annotation. Falling back to VolumeSnapshot.status.restoreSize can create a PVC with an unexpected size.

For NFS snapshots without the annotation, the controller now makes the situation explicit and requires the user to provide the desired disk size before provisioning continues.

What is the expected result?

1. Create a VirtualDisk from a legacy VirtualDiskSnapshot whose VolumeSnapshot has no vd-original-size annotation.
2. If the snapshot StorageClass provisioner is nfs.csi.k8s.io and spec.persistentVolumeClaim.size is not set, verify that:
   • PVC is not created;
   • VirtualDisk remains in Pending;
   • Ready=False with ProvisioningNotStarted reason;
   • SnapshotSizeFallback=True with LegacyNFSVolumeSnapshot reason;
   • DataSourceImportFallback warning event is emitted.
3. Specify spec.persistentVolumeClaim.size and verify that provisioning continues.
4. Verify that non-NFS snapshots keep the previous fallback behavior.

Checklist

• The code is covered by unit tests.
• e2e tests passed.
• Documentation updated according to the changes.
• Changes were tested in the Kubernetes cluster manually.

Changelog entries

section: vd
type: fix
summary: Require explicit VirtualDisk size when restoring legacy NFS snapshots without original size metadata.