chore(sos-form): add capacity to room dropdown

src/backoffice/templates/backoffice/sos_create_edit.html

@@ -181,6 +181,7 @@
                         {% if form.room.value|ensure_uuid == r.id %}selected aria-selected="true"{% endif %}>
                   {{ r.name }}
                   {% if r.assembly_id != event.assembly_id %}<span class="text-muted">({{ r.assembly.slug }})</span>{% endif %}
+                  {% if r.capacity %}<span class="text-muted">[{{ r.capacity }} seats]</span>{% endif %}
                 </option>
               {% endfor %}
             </select>