[MM-13704] Updated CLI "deleter user" to also permanently delete GroupMembers associated to user (#12858)

* [MM-13704] Updated CLI to set DeleteAt in groupmemebrs

* [MM-13704] Updated Mock Test

* [MM-13704] Refactored to use current pattern to write function

* [MM-13704] Small text change

* [MM-13704] updated translation

* [MM-13704] Updated params of error function

* [MM-13704] Fixed confusion between channel and group store

* [MM-13704] Addressed PR comments

* [MM-13704] Added test case

* [MM-13704] Fixed err declaration

store/sqlstore/group_store.go

@@ -373,6 +373,13 @@ func (s *SqlGroupStore) DeleteMember(groupID string, userID string) (*model.Grou
 	return retrievedMember, nil
 }
 
+func (s *SqlGroupStore) PermanentDeleteMembersByUser(userId string) *model.AppError {
+	if _, err := s.GetMaster().Exec("DELETE FROM GroupMembers WHERE UserId = :UserId", map[string]interface{}{"UserId": userId}); err != nil {
+		return model.NewAppError("SqlGroupStore.GroupPermanentDeleteMembersByUser", "store.sql_group.permanent_delete_members_by_user.app_error", map[string]interface{}{"UserId": userId}, "", http.StatusInternalServerError)
+	}
+	return nil
+}
+
 func (s *SqlGroupStore) CreateGroupSyncable(groupSyncable *model.GroupSyncable) (*model.GroupSyncable, *model.AppError) {
 	if err := groupSyncable.IsValid(); err != nil {
 		return nil, err