Wrap the SQLite error "interrupted (9)". That error is (as far as I
could figure out) caused by the context being closed. Unfortunately
there is no wrapping of the underlying context error, so it's not
possible to determine whether it was due to a 'deadline exceeded' error
or another cancellation cause (like upstream HTTP connection closing).
Primarily this makes a rather unreliable unit test properly reliable.
The code under test could return either `context.DeadlineExceeded` or
the "interrupted (9)" error (GORM + SQLite doesn't reliably chose one or
the other), and now this is cleanly tested for.
This is a bit more work than other queries, as it also breaks apart the
fetching of the job and the worker into separate ones. In other words,
internally the persistence layer API changes.
Just as a safety measure, before deleting a job, check that foreign key
constraints are enabled. These are optional in SQLite, and the deletion
function assumes that they are on.
As it was decided that the name "tags" would be better for the clarity
of the feature, all files and code named "cluster" or "worker cluster"
have been removed and replaced with "tag" and "worker tag". This is only
a name change, no other features were touched.
This addresses part of #104204.
Reviewed-on: https://projects.blender.org/studio/flamenco/pulls/104223
As a note to anyone who already ran a pre-release version of Flamenco
and configured some worker clusters, with the help of an SQLite client
you can migrate the clusters to tags. First build Flamenco Manager and
start it, to create the new database schema. Then run these SQL queries
via an sqlite commandline client:
```sql
insert into worker_tags
(id, created_at, updated_at, uuid, name, description)
select id, created_at, updated_at, uuid, name, description
from worker_clusters;
insert into worker_tag_membership (worker_tag_id, worker_id)
select worker_cluster_id, worker_id from worker_cluster_membership;
```
Avoid users of the persistence layer to have to test against Gorm errors,
by wrapping job/task errors in a new `PersistenceError` struct.
Instead of testing for `gorm.ErrRecordNotFound`, code can now test for
`persistence.ErrJobNotFound` or `persistence.ErrTaskNotFound`.
