[GITEA] notifies admins on new user registration (squash) DeleteByID

trivial conflict because of
   778ad795fd Refactor deletion (#28610)

(cherry picked from commit 05682614e5)
(cherry picked from commit 64bd374803)

services/mailer/mail_admin_new_user_test.go

@@ -40,7 +40,7 @@ func getTestUsers(t *testing.T) []*user_model.User {
 
 func cleanUpUsers(ctx context.Context, users []*user_model.User) {
 	for _, u := range users {
-		db.DeleteByID(ctx, u.ID, new(user_model.User))
+		db.DeleteByID[user_model.User](ctx, u.ID)
 	}
 }