Add request language listener to set locale based on language headers

src/EventListener/RequestLanguageListener.php

@@ -0,0 +1,21 @@
+<?php
+
+namespace App\EventListener;
+
+use Symfony\Component\EventDispatcher\Attribute\AsEventListener;
+use Symfony\Component\HttpKernel\Event\RequestEvent;
+use Symfony\Component\HttpKernel\KernelEvents;
+
+#[AsEventListener(event: KernelEvents::REQUEST, method: 'processLanguage', priority: 101)]
+final class RequestLanguageListener
+{
+    public function processLanguage(RequestEvent $event): void
+    {
+        $request = $event->getRequest();
+
+        $contentLanguage = $request->headers->get('Content-Language');
+        if ($contentLanguage !== null) {
+            $request->setLocale($contentLanguage);
+        }
+    }
+}