allow setting custom route for redirect controller

src/ContaoManager/Plugin.php

@@ -26,7 +26,7 @@ public function getBundles(ParserInterface $parser): array
 
     public function getRouteCollection(LoaderResolverInterface $resolver, KernelInterface $kernel)
     {
-        $routes = __DIR__ . '/../Resources/config/routes.yaml';
+        $routes = __DIR__ . '/../Resources/config/routing.yaml';
 
         return $resolver->resolve($routes)->load($routes);
     }

src/Controller/RedirectController.php

@@ -12,19 +12,18 @@
 use Symfony\Component\HttpFoundation\RedirectResponse;
 use Symfony\Component\HttpFoundation\Request;
 use Symfony\Component\HttpFoundation\Response;
+use Symfony\Component\Routing\RouterInterface;
 
 class RedirectController
 {
-    public function __invoke(Request $request, ContaoFramework $framework): Response
+    public function __invoke(Request $request, ContaoFramework $framework, RouterInterface $router): Response
     {
         // required for REQUEST_TOKEN to be defined
         $framework->initialize();
+        $url = $router->generate('contao_backend');
 
         if ($srcQuery = $request->getQueryString()) {
-            $targetQuery = str_replace('/redirect', '', Backend::addToUrl($srcQuery));
-            $url = '/' . StringUtil::ampersand($targetQuery, false);
-        } else {
-            $url = '/contao';
+            $url = StringUtil::ampersand(str_replace($request->getPathInfo(), $url, '/' . Backend::addToUrl($srcQuery)), false);
         }
 
         return new RedirectResponse($url);

src/Resources/config/routes.yaml → src/Resources/config/_definition.yaml

@@ -1,3 +1,5 @@
 ameotoko_backend_redirect:
-    path: /contao/redirect
+    path: /
     controller: Ameotoko\BackendRedirect\Controller\RedirectController
+    defaults:
+        _scope: backend

src/Resources/config/routing.yaml

@@ -0,0 +1,5 @@
+_ameotoko_backend_redirect:
+    resource: './_definition.yaml'
+    prefix: /contao/redirect
+    trailing_slash_on_root: false
+