`Dossier.champs` is not really an inverse of `Champs.dossier`: when a
Champ record is created, it should not always be added to dossier.champs
(for instance if the champ is private).
NB: this breaks the workaround we added in #3907 to fix the parent
dossier not being touched in some cases (the workaround was to add an
inverse relationship, but we now have to remove it).
The new workaround is to watch for `changed_for_autosave?` on champs.
Unlike `changed?`, `changed_for_autosave?` also detects changes to
attachments. This allows us to touch both `last_champ_updated_at` and
`updated_at` in a single pass.
This line causes an error on Rails 6.1.
And it isn't even necessary: this line is supposed to query avis where
the expert advice has been requested – but this is handled by the
`if expert.dossiers.include?(self)` condition just above.
Follow-up of #5953.
Refactor the concerns with two goals:
- Getting closer from the way ActiveStorage adds its own hooks.
Usually ActiveStorage does this using an `Attachment#after_create`
hook, which then delegates to the blob to enqueue the job.
- Enqueuing each job only once. By hooking on `Attachment#after_create`,
we guarantee each job will be added only once.
We then let the jobs themselves check if they are relevant or not, and
retry or discard themselves if necessary.
We also need to update the tests a bit, because Rails'
`perform_enqueued_jobs(&block)` test helper doesn't honor the `retry_on`
clause of jobs. Instead it forwards the exception to the caller – which
makes the test fail.
Instead we use the inline version of `perform_enqueued_jobs()`, without
a block, which properly ignores errors catched by retry_on.
