user_groups: Track acting user for remove_subgroups_from_user_group.

This is a prep-commit for populating RealmAuditLogs for changes made to
UserGroup.

Signed-off-by: Zixuan James Li <p359101898@gmail.com>

zerver/actions/user_groups.py

@@ -215,7 +215,9 @@ def add_subgroups_to_user_group(
 
 
 @transaction.atomic
-def remove_subgroups_from_user_group(user_group: UserGroup, subgroups: List[UserGroup]) -> None:
+def remove_subgroups_from_user_group(
+    user_group: UserGroup, subgroups: List[UserGroup], *, acting_user: Optional[UserProfile]
+) -> None:
     GroupGroupMembership.objects.filter(supergroup=user_group, subgroup__in=subgroups).delete()
 
     subgroup_ids = [subgroup.id for subgroup in subgroups]

zerver/tests/test_events.py

@@ -1324,7 +1324,9 @@ class NormalActionsTest(BaseAction):
         check_user_group_add_subgroups("events[0]", events[0])
 
         # Test remove subgroups
-        events = self.verify_action(lambda: remove_subgroups_from_user_group(backend, [api_design]))
+        events = self.verify_action(
+            lambda: remove_subgroups_from_user_group(backend, [api_design], acting_user=None)
+        )
         check_user_group_remove_subgroups("events[0]", events[0])
 
         # Test remove event

zerver/views/user_groups.py

@@ -195,7 +195,7 @@ def remove_subgroups_from_group_backend(
                 )
             )
 
-    remove_subgroups_from_user_group(user_group, subgroups)
+    remove_subgroups_from_user_group(user_group, subgroups, acting_user=user_profile)
     return json_success(request)