Feature: #99234 - Dynamic URL parts in TYPO3 backend URLs

See forge#99234

Description

TYPO3's backend URL routing now uses Symfony's routing component for resolving and generating URLs.

This way, it is possible for extension authors to register backend routes with path segments that contain dynamic parts, which are then resolved into a request attribute called "routing".

These routes are defined within the route path as named placeholders.

Impact

It is possible to define routes with placeholders in an extension's Routes.php:

return [
    'my_route' => [
        'path' => '/rollback-item/{identifier}',
        'target' => \MyVendor\MyPackage\Controller\RollbackController::class . '::handle',
    ],
];

Within the controller:

public function handle(ServerRequestInterface $request): ResponseInterface
{
    $routing = $request->getAttribute('routing');
    $myIdentifier = $routing['identifier'];
    $route = $routing->getRoute();
    // ...
}