There are still issues with foreign keys getting disabled, so enable them
in the periodic database consistency check.
A more permanent solution is likely to drop GORM and switch to something
else that gives us an on-connect-callback, which can then be used to
turn on foreign key constraints for every connection made.
Deleting jobs from the database can still sometimes cause consistency
errors, as if foreign key constraints aren't enabled. This check is there
to try and get a grip on things.
Instead of always performing the periodic integrity check, make it possible
to disable it or run it at different intervals.
Currently for the Blender Studio it's crunch time, so the check should
really only run when there is someone looking at the system (i.e. at
restarts for upgrade purposes).
Perform these two SQL calls & check their result:
- `PRAGMA integrity_check`
- `PRAGMA foreign_key_check`:
See https: //www.sqlite.org/pragma.html for more info on these.
This also removes the unused `PeriodicMaintenanceLoop()` function.
Periodic checking while Flamenco Manager is running might be introduced
in a future commit, after the startup-time checks have been shown to not
get in the way.
