#146 Team leave

* adds button and functionality for leaving a team
   * if the admin leaves the team, another user will be chosen as new admin automatically
* improves Team (django) admin backend
   * better control over user adding-removing
   * only added team members are selectable as admin

user/views.py

@@ -13,7 +13,7 @@ from django.utils.translation import gettext_lazy as _
 from konova.contexts import BaseContext
 from konova.decorators import any_group_check, default_group_required
 from user.forms import UserNotificationForm, UserContactForm, UserAPITokenForm, NewTeamModalForm, EditTeamModalForm, \
-    RemoveTeamModalForm, TeamDataForm
+    RemoveTeamModalForm, TeamDataForm, LeaveTeamModalForm
 
 
 @login_required
@@ -204,3 +204,24 @@ def remove_team_view(request: HttpRequest, id: str):
         _("Team removed"),
         redirect_url=reverse("user:team-index")
     )
+
+
+@login_required
+def leave_team_view(request: HttpRequest, id: str):
+    team = get_object_or_404(Team, id=id)
+    user = request.user
+
+    is_user_team_member = team.users.filter(id=user.id).exists()
+    if not is_user_team_member:
+        messages.info(
+            request,
+            _("You are not a member of this team")
+        )
+        return redirect("user:team-index")
+
+    form = LeaveTeamModalForm(request.POST or None, instance=team, request=request)
+    return form.process_request(
+        request,
+        _("Left Team"),
+        redirect_url=reverse("user:team-index")
+    )