Silex フレームワークを使用して Web サービスに認証を提供するにはどうすればよいですか?

{
    "require": {
        "silex/silex": "~2.0",
        "symfony/security": "^4.3"
    },
    "autoload": {
        "psr-4": { "": "src/" }
    }
}

use SymfonyComponentSecurityCoreUserInMemoryUserProvider;
use SymfonyComponentSecurityCoreUserUser;
use SymfonyComponentSecurityCoreUserUserProviderInterface;

$app->register(new SilexProviderSecurityServiceProvider());

$app['security.firewalls'] = array(
    'secured' => array(
        'pattern' => '^/secured',
        'http' => true,
        'users' => function() use($app){
            return new InMemoryUserProvider(
                array(
                    'admin' => array('ROLE_USER', 'password')
                )
            );
        }
    )
);

$app['security.access_rules'] = array(
    array('^/secured', 'ROLE_USER')
);

$app['security.role_hierarchy'] = array(
    'ROLE_ADMIN' => array('ROLE_USER')
);

$app['security.user_provider'] = function($app) {
    return new UserProvider($app['db']);
};

$app['security.encoder.bcrypt'] = $app->share(function($app) {
    return new BCryptPasswordEncoder($app['security.encoder.bcrypt.cost']);
});

$app['security.authentication_listener.factory.form'] = $app->protect(function ($name, $options) use ($app) {
    $app['security.authentication_provider.'.$name.'.form'] = function () use ($app) {
        return new FormAuthenticationProvider(
            $app['security.user_provider'],
            $app['security.encoder_factory']
        );
    };
 
    $app['security.authentication_listener.'.$name.'.form'] = function () use ($app, $name, $options) {
        return new FormAuthenticationListener(
            $app['security'],
            $app['security.authentication_manager'],
            $name,
            $options,
            new UsernamePasswordFormAuthenticationEntryPoint(
                $app,
                $app['security.http_utils'],
                $name
            ),
            $app['logger'],
            $app['dispatcher'],
            $app['security.authentication.session_strategy']
        );
    };
 
    return array(
        'security.authentication_provider.'.$name.'.form',
        'security.authentication_listener.'.$name.'.form',
        null,
        'pre_auth'
    );
});

use SymfonyComponentSecurityCoreUserUserProviderInterface;
use SymfonyComponentSecurityCoreUserUserInterface;
use SymfonyComponentSecurityCoreExceptionUnsupportedUserException;

class UserProvider implements UserProviderInterface
{
    private $db;

    public function __construct(Connection $db)
    {
        $this->db = $db;
    }

    public function loadUserByUsername($username)
    {
        $stmt = $this->db->executeQuery('SELECT * FROM users WHERE username = ?', array(strtolower($username)));

        if (!$user = $stmt->fetch()) {
            throw new UsernameNotFoundException(sprintf('Username "%s" does not exist.', $username));
        }

        $rolesStmt = $this->db->executeQuery('SELECT roles.role FROM user_roles JOIN roles ON user_roles.role_id = roles.id WHERE user_id = ?', array($user['id']));
        $roles = array();
        while ($role = $rolesStmt->fetch(PDO::FETCH_ASSOC)) {
            $roles[] = $role['role'];
        }

        return new User($user['username'], $user['password'], explode(',', $user['roles']), true, true, true, true);
    }

    public function refreshUser(UserInterface $user)
    {
        if (!$user instanceof User) {
            throw new UnsupportedUserException(sprintf('Instances of "%s" are not supported.', get_class($user)));
        }

        return $user;
    }

    public function supportsClass($class)
    {
        return $class === 'SymfonyComponentSecurityCoreUserUser';
    }
}

$app->match('/login', function(Request $request) use ($app){
        $username = $request->request->get('_username');
        $password = $request->request->get('_password');

        $user = $app['security.user_provider']->loadUserByUsername($username);

        if (!$app['security.encoder.bcrypt']->isPasswordValid($user->getPassword(), $password, $user->getSalt())) {
            throw new Exception('Bad credentials');
        } else {
            $token = new UsernamePasswordToken($user, null, 'secured', $user->getRoles());
            $app['security.token_storage']->setToken($token);
            $request->getSession()->set('_security_secured', serialize($token));
            return $app->redirect($request->headers->get('referer'));
        }
})->bind('login');

$app->match('/secured', function() use ($app){
        if (!$app['security.authorization_checker']->isGranted('ROLE_USER')){
            return $app->redirect('/login');
        }
 
        return 'Welcome ' . $app['security.token_storage']->getToken()->getUsername();
})->bind('secured');