Better usage of cache for groups and clubs related operations (#634)

* Better usage of cache for group retrieval

* Cache clearing on object deletion or update

* replace signals by save and delete override

* add is_anonymous check in is_owned_by

Add in many is_owned_by(self, user) methods that user is not anonymous. Since many of those functions do db queries, this should reduce a little bit the load of the db.

* Stricter usage of User.is_in_group

Constrain the parameters that can be passed to the function to make sure only a str or an int can be used. Also force to explicitly specify if the group id or the group name is used.

* write test and correct bugs

* remove forgotten populate commands

* Correct test

club/forms.py

@@ -229,9 +229,7 @@ class ClubMemberForm(forms.Form):
                 id__in=[
                     ms.user.id
                     for ms in self.club_members
-                    if ms.can_be_edited_by(
-                        self.request_user, self.request_user_membership
-                    )
+                    if ms.can_be_edited_by(self.request_user)
                 ]
             ).all(),
             label=_("Mark as old"),