Hard deprecate not passing a user to WikiPage::getCreator when needed

If $audience is FOR_USER, user is needed

Bug: T248291
Change-Id: Idc4429baa7f7f2a028eb5378d8e2c2a32f1d3761

RELEASE-NOTES-1.35

@@ -599,6 +599,8 @@ because of Phabricator reports.
   - LogEventsList::userCanViewLogType
   - LogEventsList::getExcludeClause (only used when the 'audience' parameter
      is set to something other than the default of 'public')
+  - WikiPage::getCreator (only when the 'audience' parameter is set to
+     Revision::FOR_THIS_USER)
   - LogPage::addEntry
   - FileDeleteForm::doDelete
   - OldLocalFile::userCan

includes/page/WikiPage.php

@@ -837,12 +837,20 @@ class WikiPage implements Page, IDBAccessObject {
 	 *   Revision::FOR_THIS_USER    to be displayed to the given user
 	 *   Revision::RAW              get the text regardless of permissions
 	 * @param User|null $user User object to check for, only if FOR_THIS_USER is passed
-	 *   to the $audience parameter
+	 *   to the $audience parameter (not passing for FOR_THIS_USER is deprecated since 1.35)
 	 * @return User|null
 	 */
 	public function getCreator( $audience = RevisionRecord::FOR_PUBLIC, User $user = null ) {
 		$revision = $this->getOldestRevision();
 		if ( $revision ) {
+			if ( $audience === RevisionRecord::FOR_THIS_USER && $user === null ) {
+				wfDeprecated(
+					__METHOD__ . ' using FOR_THIS_USER without a user',
+					'1.35'
+				);
+				global $wgUser;
+				$user = $wgUser;
+			}
 			$userName = $revision->getUserText( $audience, $user );
 			return User::newFromName( $userName, false );
 		} else {