How to use a separate authentication or Application.php

Need Help
3

This is my approach to do this :

in config/routes.php

$routes->prefix(
    'Backend',
    ['path' => '/gestion', '_namePrefix' => 'backend:'],
    function (RouteBuilder $builder) {
        $authenticationService = new AuthenticationService();
        $fields = [
            IdentifierInterface::CREDENTIAL_USERNAME => 'email',
            IdentifierInterface::CREDENTIAL_PASSWORD => 'password',
        ];
        $authenticationService->loadAuthenticator(SessionAuthenticator::class);
        $authenticationService->loadAuthenticator(FormAuthenticator::class, [
            'fields' => $fields,
            'loginUrl' => ['_name' => 'backend:auth:login'],
        ]);

        $builder->registerMiddleware('authentication', new AuthenticationMiddleware($authenticationService));
        $builder->applyMiddleware('authentication');

In your Prefix App Controller:

    public function initialize(): void
    {
        parent::initialize();

        $service = $this->request->getAttribute('authentication');
        $service->setConfig([
            'unauthenticatedRedirect' => Router::url(['_name' => 'backend:auth:login']),
            'queryParam' => 'r',
        ]);

        $this->loadComponent('Authentication.Authentication');
    }

You can use one AuthenticationService by prefix, configured as you want.