Normalize the datetime format of received activity before DB insertion in ActivityPub\Processor

- Restore private message storage

src/Protocol/ActivityPub/Processor.php

@@ -142,7 +142,7 @@ class Processor
 		}
 
 		$item['changed'] = DateTimeFormat::utcNow();
-		$item['edited'] = $activity['updated'];
+		$item['edited'] = DateTimeFormat::utc($activity['updated']);
 
 		$item = self::processContent($activity, $item);
 		if (empty($item)) {
@@ -382,8 +382,8 @@ class Processor
 
 		$item['uri'] = $activity['id'];
 
-		$item['created'] = $activity['published'];
-		$item['edited'] = $activity['updated'];
+		$item['created'] = DateTimeFormat::utc($activity['published']);
+		$item['edited'] = DateTimeFormat::utc($activity['updated']);
 		$item['guid'] = $activity['diaspora:guid'];
 
 		$item = self::processContent($activity, $item);