Workers can now be soft-deleted. Tasks assigned to the worker will remain
associated with that Worker. Active tasks will be re-queued so other
workers can pick them up.
The Task details component already linked to the Worker it was assigned
to last, and now the Worker links back to the task.
There's only one task shown in the Worker details. If the Worker is
actively working on a task, that one's shown. Otherwise it's the
last-updated task that was assigned to the worker.
`persistence.Model` contains the common database fields for most model
structs. It is a copy of `gorm.Model`, but without the `DeletedAt`
field (which triggers Gorm's soft deletion).
Soft deletion is not used by Flamenco. If it ever becomes necessary to
support soft-deletion, see https://gorm.io/docs/delete.html#Soft-Delete
Update the 'last seen at' timestamp of workers when they:
- sign on
- sign off
- get a task assigned
- send a task update
- check whether they can keep running their task
Note that this commit is necessary to not have the workers time out
immediately ;-)
The add-on code was copy-pasted from other addons and used the GPL v2
license, whereas by accident the LICENSE text file had the GNU "Affero" GPL
license v3 (instead of regular GPL v3).
This is now all streamlined, and all code is licensed as "GPL v3 or later".
Furthermore, the code comments just show a SPDX License Identifier
instead of an entire license block.
Instead of returning an error "error doing X", just return "doing X". The
fact that it's returned as an error object says enough about that it's
an error.
This also makes it easier to chain error messages, without seeing the
word "error" in every part of the chain.
Where the PostgreSQL DB migration code could handle `NOT NULL` columns just
fine, SQLite has less table-altering functionality. As a result, migrations
have to copy entire database tables, which doesn't play well with
not-nullable columns.
