Add AbstractController, implement flash message handling, and refactor repositories

src/Controller/AbstractController.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Controller;
+
+use App\Enum\FlashType;
+use Symfony\Bundle\FrameworkBundle\Controller\AbstractController as AbstractBaseController;
+
+abstract class AbstractController extends AbstractBaseController
+{
+    protected function addFlash(FlashType|string $type, mixed $message): void
+    {
+        if ($type instanceof FlashType) {
+            $type = $type->value;
+        }
+        parent::addFlash($type, $message);
+    }
+}