The ResticIdentifier field in BackupRepository is only relevant for restic
repositories. For kopia repositories, this field is unused and should be
omitted. This change:
- Adds omitempty tag to ResticIdentifier field in BackupRepository CRD
- Updates controller to only populate ResticIdentifier for restic repos
- Adds tests to verify behavior for both restic and kopia repository types
This ensures backward compatibility while properly handling kopia repositories
that don't require a restic-compatible identifier.
Signed-off-by: Tiger Kaovilai <tkaovila@redhat.com>