implement CopyLanguageContent

This event is meant to give 3rd-party developers the possibility to copy i18n contents in every case contents should be copied to another language.

wcfsetup/install/files/lib/data/language/LanguageEditor.class.php

@@ -11,8 +11,10 @@
 use wcf\data\page\PageEditor;
 use wcf\system\cache\builder\LanguageCacheBuilder;
 use wcf\system\database\util\PreparedStatementConditionBuilder;
+use wcf\system\event\EventHandler;
 use wcf\system\exception\SystemException;
 use wcf\system\io\AtomicWriter;
+use wcf\system\language\event\CopyLanguageContent;
 use wcf\system\language\LanguageFactory;
 use wcf\system\Regex;
 use wcf\system\WCF;
@@ -1054,5 +1056,10 @@ public static function copyLanguageContent($sourceLanguageID, $destinationLangua
         }
 
         PageEditor::resetCache();
+
+        EventHandler::getInstance()->fire(new CopyLanguageContent(
+            LanguageFactory::getInstance()->getLanguage($sourceLanguageID),
+            LanguageFactory::getInstance()->getLanguage($destinationLanguageID)
+        ));
     }
 }

wcfsetup/install/files/lib/system/language/event/CopyLanguageContent.class.php

@@ -0,0 +1,23 @@
+<?php
+
+namespace wcf\system\language\event;
+
+use wcf\data\language\Language;
+use wcf\system\event\IEvent;
+
+/**
+ * Indicates that the contents of a language should be copied to another one.
+ *
+ * @author Florian Gail
+ * @copyright 2001-2023 WoltLab GmbH
+ * @license GNU Lesser General Public License <http://opensource.org/licenses/lgpl-license.php>
+ * @since 6.0
+ */
+final class CopyLanguageContent implements IEvent
+{
+    public function __construct(
+        public readonly Language $sourceLanguage,
+        public readonly Language $targetLanguage,
+    ) {
+    }
+}