Still implement deprecated username method

This updates the makers for symfony/symfony#41493

Author: wouterj

src/Resources/skeleton/security/UserProvider.tpl.php

@@ -28,6 +28,16 @@ public function <?= $uses_user_identifier ? 'loadUserByIdentifier($identifier)'
         throw new \Exception('TODO: fill in <?= $uses_user_identifier ? 'loadUserByIdentifier()' : 'loadUserByUsername()' ?> inside '.__FILE__);
     }
 
+<?php if ($uses_user_identifier) : ?>
+    /**
+     * @deprecated since Symfony 5.3, loadUserByIdentifier() is used instead
+     */
+    public function loadUserByUsername($username): UserInterface
+    {
+        return $this->loadUserByIdentifier($username);
+    }
+<?php endif ?>
+
     /**
      * Refreshes the user after being reloaded from the session.
      *

src/Security/UserClassBuilder.php

@@ -103,6 +103,16 @@ private function addGetUsername(ClassSourceManipulator $manipulator, UserClassCo
         // Check if we're using Symfony 5.3+ - UserInterface::getUsername() was replaced with UserInterface::getUserIdentifier()
         if (class_exists(InMemoryUser::class)) {
             $getterIdentifierName = 'getUserIdentifier';
+
+            // also add the deprecated getUsername method
+            $manipulator->addAccessorMethod(
+                $userClassConfig->getIdentityPropertyName(),
+                'getUsername',
+                'string',
+                false,
+                ['@deprecated since Symfony 5.3, use getUserIdentifier instead'],
+                true
+            );
         }
 
         // define getUsername (if it was defined above, this will override)