docs: Add api.php to "API" doc group

Follow-up bc1f601382, which added a group to load.php, but I forgot
to add api.php to its group.

Also, fix the pre-existing group that thumb.php and thumb_handler.php
were a part of. It looks like the entire "Media" group was not
defined anywhere, so it was ignored by Doxygen. This is now fixed.

Change-Id: Iba487aac5883f66b81f2496a38a3c978d5e6600b

api.php

@@ -30,6 +30,7 @@
  *
  * @file
  * @ingroup entrypoint
+ * @ingroup API
  */
 
 use MediaWiki\Logger\LegacyLogger;

includes/media/MediaHandler.php

@@ -1,7 +1,5 @@
 <?php
 /**
- * Media-handling base classes and generic functionality.
- *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
@@ -22,6 +20,13 @@
  */
 use MediaWiki\MediaWikiServices;
 
+/**
+ * @defgroup Media Media
+ *
+ * Media handlers and other classes relating to Multimedia support,
+ * with the exception of FileRepo and FileBackend, which have their own groups.
+ */
+
 /**
  * Base media handler class
  *

thumb.php

@@ -21,8 +21,8 @@
  * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
- * @ingroup Media
  * @ingroup entrypoint
+ * @ingroup Media
  */
 
 use MediaWiki\Logger\LoggerFactory;

thumb_handler.php

@@ -22,8 +22,8 @@
  * http://www.gnu.org/copyleft/gpl.html
  *
  * @file
- * @ingroup Media
  * @ingroup entrypoint
+ * @ingroup Media
  */
 
 define( 'THUMB_HANDLER', true );