Merge pull request #51467 from nextcloud/backport/51441/stable30

[stable30] fix(CalDav): alter invitation attachment filename and type

Author: SebastianKrupinski

apps/dav/lib/CalDAV/Schedule/IMipPlugin.php

@@ -289,8 +289,8 @@ public function schedule(Message $iTipMessage) {
 				$message->setBodyHtml($template->renderHtml());
 				$message->setAttachments((new \OCP\Mail\Provider\Attachment(
 					$itip_msg,
-					'event.ics',
-					'text/calendar; method=' . $iTipMessage->method,
+					null,
+					'text/calendar; name=event.ics; method=' . $iTipMessage->method,
 					true
 				)));
 				// send message