Before, when autosaving a draft, removing a repetition row would
send `_destroy` inputs to the controller – but not remove the row
from the DOM. This led to the `_destroy` inputs being sent again
on the next autosave request, which made the controller raise
(because the row fields were already deleted before).
To fix this, we let the controller response remove the deleted
row(s) from the DOM.
Doing it using a controller response avoids the need to keep track
of operations on the Javascript side: the controller can easily
know which row was just deleted, and emit the relevant changes for
the DOM. This keeps the autosave requests robust: even if a request
is skipped (e.g. because of a network interruption), the next request
will still contain the relevant informations to succeed, and not let the
form in an unstable state.
Fix#5470
In repetitions we can't render the piece_justificative champ in the way
we do for normal champs (which was already a bit hackish).
Instead we render the whole form partial – and then extract the champ
from the form. In this way, we're sure to render the champ as it
appears in the form, without any hacks to reproduce the form structure.
