#1467 Implement messages file migration

- Create messages updater called when a messages YML file is loaded
  - Work in progress
- Does not yet include changes to any message keys

src/main/java/fr/xephi/authme/message/MessagesFileHandler.java

@@ -1,5 +1,8 @@
 package fr.xephi.authme.message;
 
+import fr.xephi.authme.ConsoleLogger;
+import fr.xephi.authme.message.updater.MessageUpdater;
+
 import javax.inject.Inject;
 
 /**
@@ -7,10 +10,35 @@ import javax.inject.Inject;
  */
 public class MessagesFileHandler extends AbstractMessageFileHandler {
 
-    @Inject // Trigger injection in the superclass
+    // TODO #1467: With the migration the messages handler has become so different that it would be worth
+    // to remove the extension and extract common features into a helper class instead
+
+    @Inject
+    private MessageUpdater messageUpdater;
+
     MessagesFileHandler() {
     }
 
+    @Override
+    public void reload() {
+        reloadInternal(false);
+    }
+
+    private void reloadInternal(boolean isFromReload) {
+        super.reload();
+
+        String language = getLanguage();
+        boolean hasChange = messageUpdater.migrateAndSave(
+            getUserLanguageFile(), createFilePath(language), createFilePath(DEFAULT_LANGUAGE));
+        if (hasChange) {
+            if (isFromReload) {
+                ConsoleLogger.warning("Migration after reload attempt");
+            } else {
+                reloadInternal(true);
+            }
+        }
+    }
+
     @Override
     protected String createFilePath(String language) {
         return "messages/messages_" + language + ".yml";