www.apply: fix htmx swap when accept confirmation fails

It's quite unlikely to fail since the modal is only shown when the forms
are valid.
However:
- with the help of some JS (:wave: 71a19fc),
- or if the form is submitted at 23:59 with hiring_start_at=today,
  the modal might be shown but the confirmation might happen the next day
  returning an error

In such case, the htmx swap produced a mess with the complete page
inserted inside the modal: let's fix that.

itou/templates/apply/includes/accept_section.html

@@ -16,7 +16,7 @@ <h3 class="modal-title" id="confirmation-modal-label">Confirmation de l’embauc
             </div>
             <div class="modal-footer">
                 <button type="button" class="btn btn-sm btn-outline-primary" data-bs-dismiss="modal">Retour</button>
-                <button class="btn btn-sm btn-primary" hx-post={{ request.path }} hx-vals='{"confirmed": "True"}' hx-include="#acceptForm" {% matomo_event "candidature" "submit" "accept_application_confirmation" %}>Confirmer
+                <button class="btn btn-sm btn-primary" hx-post={{ request.path }} hx-target="#acceptFormDiv" hx-swap="outerHTML" hx-vals='{"confirmed": "True"}' hx-include="#acceptForm" {% matomo_event "candidature" "submit" "accept_application_confirmation" %} data-bs-dismiss="modal">Confirmer
                 </button>
             </div>
         </div>

itou/templates/apply/includes/job_application_accept_form.html

@@ -3,7 +3,7 @@
 {% load matomo %}
 {% load buttons_form %}
 
-<div class="c-form">
+<div class="c-form" id="acceptFormDiv">
     <form id="acceptForm" method="post" hx-post="{{ request.path }}" hx-swap="outerHTML show:#acceptForm:top" hx-select="#acceptForm" class="js-format-nir">
         {% if has_form_error %}
             <div class="alert alert-danger">

itou/www/apply/views/common.py

@@ -187,6 +187,9 @@ def _accept(request, siae, job_seeker, error_url, back_url, template_name, extra
 
         return HttpResponseClientRedirect(final_url)
 
+    if request.htmx:
+        template_name = "apply/includes/job_application_accept_form.html"
+
     return render(request, template_name, {**context, "has_form_error": any(form.errors for form in forms)})