Fix reported error when clicking on the CERN Infrastructure link in...

Fix reported error when clicking on the CERN Infrastructure link in Configuration when using a language prefix url.
https://drupal-community.web.cern.ch/t/broken-link-to-cern-infrastructure-in-french/737/2

cern_integration.info.yml

@@ -2,7 +2,7 @@ name: CERN Integration module
 description: Custom functionality and constraints for CERN Drupal infrastructure
 package: CERN
 type: module
-version: '8.0.8'
+version: '8.0.9'
 core: 8.x
 
-required: TRUE
\ No newline at end of file
+required: TRUE

cern_integration.routing.yml

@@ -2,5 +2,6 @@ cern_integration.settings:
   path: '/_site'
   defaults:
     _title: 'CERN Infrastructure'
+    _controller: '\Drupal\cern_integration\Controller\BackendController::redirect'
   requirements:
     _permission: 'administer site configuration'

src/Controller/BackendController.php

+<?php
+
+namespace Drupal\cern_integration\Controller;
+
+use Drupal\Core\Controller\ControllerBase;
+use Symfony\Component\HttpFoundation\RedirectResponse;
+
+/**
+ * An example controller.
+ */
+class BackendController extends ControllerBase {
+
+  /**
+   * Returns a render-able array for a test page.
+   */
+  public function redirect() {
+     return new RedirectResponse("/_site");
+  }
+
+}
+