code: public function getRouteCollection(LoaderResolverInterface $resolver, KernelInterface $kernel): ?RouteCollection
      {
          if ('dev' !== $kernel->getEnvironment()) {
              return null;
          }
  
          $collections = [];
  
          $files = [
              '_wdt' => '@WebProfilerBundle/Resources/config/routing/wdt.xml',
              '_profiler' => '@WebProfilerBundle/Resources/config/routing/profiler.xml',
          ];
  
          foreach ($files as $prefix => $file) {
              /** @var RouteCollection $collection */
              $collection = $resolver->resolve($file)->load($file);
              $collection->addPrefix($prefix);
  
              $collections[] = $collection;
          }
  
          $collection = array_reduce(
              $collections,
              static function (RouteCollection $carry, RouteCollection $item): RouteCollection {
                  $carry->addCollection($item);
  
                  return $carry;
              },
              new RouteCollection()
          );
  
          // Redirect the deprecated install.php file
          $collection->add(
              'contao_install_redirect',
              new Route(
                  '/install.php',
                  [
                      '_scope' => 'backend',
                      '_controller' => 'Symfony\Bundle\FrameworkBundle\Controller\RedirectController::redirectAction',
                      'route' => 'contao_install',
                      'permanent' => true,
                  ]
              )
          );
  
          return $collection;
      }
docs: {@inheritdoc}