Add a file name and namespace to the code example

Author: Sander De la Marche

components/http_foundation.rst

@@ -717,7 +717,11 @@ UrlHelper
 
 Generating absolute (and relative) URLs for a given path is a common need in lots of applications. In Twig templates this is trivial thanks to the absolute_url() and relative_path() functions. The same functionality can be found in the :class:`Symfony\\Component\\HttpFoundation\\UrlHelper` class, which can be injected as a service anywhere in your application. This class provides two public methods called getAbsoluteUrl() and getRelativePath()::
 
-    Use Symfony\Component\HttpFoundation\UrlHelper;
+    // src/Normalizer/UserApiNormalizer.php
+
+    namespace App\Normalizer;
+
+    use Symfony\Component\HttpFoundation\UrlHelper;
 
     class UserApiNormalizer
     {