Note that this is "bleeding edge" functionality and that the newly added
config option PHOTOPRISM_BACKUP_RETAIN can be set, but does not have any
effect yet. Feedback welcome!
Signed-off-by: Michael Mayer <michael@photoprism.app>
In the next step, this worker can be configured to automatically create
index and/or album backups at regular intervals.
Signed-off-by: Michael Mayer <michael@photoprism.app>