Offline storage

[dswd]

It would be helpful if bundles do not always have to be available during zvault execution, especially during operations that do not need them.
It should be possible to move bundles to offline storage, mark them as stored offline and not treat them as absent even if they are not found on remote storage.
The offline bundles that exist should be stored in list files that contain

• The complete bundle header
• The list of chunks contained in these bundles

Implementation steps:

• Format for offline bundle lists containing header and contents
• track command that scans "offline" folder and creates an offline bundle list from all bundles found there.
• untrack command that removes an offline storage by its id.
• Read all offline bundle lists and treat those bundles like bundles on remote storage
• On data access, error out and ask user to load the required bundle from offline storage.