Delete related notifications on issue deletion too (#18953)

* use .Decr for issue comment counting

* Remove notification on issue removal

models/issue.go

@@ -2124,6 +2124,7 @@ func deleteIssue(ctx context.Context, issue *Issue) error {
 		&IssueDependency{},
 		&IssueAssignees{},
 		&IssueUser{},
+		&Notification{},
 		&Reaction{},
 		&IssueWatch{},
 		&Stopwatch{},

models/issue_comment.go

@@ -1163,7 +1163,7 @@ func deleteComment(e db.Engine, comment *Comment) error {
 	}
 
 	if comment.Type == CommentTypeComment {
-		if _, err := e.Exec("UPDATE `issue` SET num_comments = num_comments - 1 WHERE id = ?", comment.IssueID); err != nil {
+		if _, err := e.ID(comment.IssueID).Decr("num_comments").Update(new(Issue)); err != nil {
 			return err
 		}
 	}