Use application_role.id to reference users in team page forms.

Membership in a resource should be decoupled from the users table.

templates/fragments/applications/edit_team.html

@@ -92,7 +92,7 @@
           {% endif %}
         </div>
       {% endcall %}
-      {{ member_form.user_id() }}
+      {{ member_form.role_id() }}
     </li>
   </toggler>
 {% endfor %}