Add initial set of files

src/Kernel.php

@@ -0,0 +1,19 @@
+<?php
+
+namespace App;
+
+use Symfony\Bundle\FrameworkBundle\Kernel\MicroKernelTrait;
+use Symfony\Component\HttpKernel\Kernel as BaseKernel;
+
+class Kernel extends BaseKernel
+{
+    use MicroKernelTrait;
+
+    /**
+     * @return list<string> An array of allowed values for APP_ENV
+     */
+    private function getAllowedEnvs(): array
+    {
+        return ['prod', 'dev', 'test'];
+    }
+}