Merge pull request #13647 from MrPetovan/bug/10369-rss-group-ns

Add expected xmlns attribute to group feed entries

src/Protocol/OStatus.php

@@ -1470,6 +1470,8 @@ class OStatus
 			$entry = $doc->createElement('entry');
 
 			if ($owner['contact-type'] == Contact::TYPE_COMMUNITY) {
+				$entry->setAttribute('xmlns:activity', ActivityNamespace::ACTIVITY);
+
 				$contact = Contact::getByURL($item['author-link']) ?: $owner;
 				$contact['nickname'] = $contact['nickname'] ?? $contact['nick'];
 				$author = self::addAuthor($doc, $contact, false);