format is part of the backup target
in the future, if we want per-app format or schedule, we can add this
separately to the apps table itself. the full box backup can ignore
apps with a set backup target and use the latest backup (like an errored app).
the nice thing is restore will work correctly.
this is useful for clone also to copy notes, operators, checklist
of the time when the backup was made (as opposed to current)
at this point, it's not clear why we need a archives table. it's
an optimization to not have to store icon for every backup.
Cleaner to separate things from the backups table.
* icon, appConfig, appStoreIcon etc are only valid for archives
* older version cloudron does not have appConfig in backups table (so it
cannot be an archive entry)
One idea was to compute this at cleanup time, but this has two problems:
* the UI won't reflect this value. can be good or bad
* the cleaner has no easy way to find out the "parent". I guess we should
change our data structure, if we want to go down this route...
the main motivation is that id can be used in REST API routes. previously,
the id was a path and this had a "/" in it. This made /api/v1/backups/:backupId
not work.
