如果我扩展AbstractFormLoginAuthenticator，如何在Symfony4中使用电子邮件代替用户名？

use Symfony\Component\Security\Guard\AbstractFormLoginAuthenticator;
use Symfony\Component\HttpFoundation\Request;
use Symfony\Component\Security\Core\User\UserProviderInterface;
use Symfony\Component\Security\Core\Exception\AuthenticationException;
use Symfony\Component\Security\Core\User\UserInterface;
use Symfony\Component\Security\Core\Encoder\UserPasswordEncoderInterface;

class EmailFormLoginAuthenticator extends AbstractFormLoginAuthenticator
{
    // 实现需要的方法...
}

class EmailFormLoginAuthenticator extends AbstractFormLoginAuthenticator
{
    public function getCredentials(Request $request)
    {
        $credentials = [
            'email' => $request->get('email'),
            'password' => $request->get('password'),
        ];

        return $credentials;
    }
}

class EmailFormLoginAuthenticator extends AbstractFormLoginAuthenticator
{
    private $userProvider;

    public function __construct(UserProviderInterface $userProvider)
    {
        $this->userProvider = $userProvider;
    }

    public function getUser($credentials, UserProviderInterface $userProvider)
    {
        $email = $credentials['email'];

        return $this->userProvider->loadUserByUsername($email);
    }
}

class EmailFormLoginAuthenticator extends AbstractFormLoginAuthenticator
{
    private $userProvider;
    private $encoder;

    public function __construct(UserProviderInterface $userProvider, UserPasswordEncoderInterface $encoder)
    {
        $this->userProvider = $userProvider;
        $this->encoder = $encoder;
    }

    public function checkCredentials($credentials, UserInterface $user)
    {
        $password = $credentials['password'];

        if ($this->encoder->isPasswordValid($user, $password)) {
            return true;
        }

        throw new AuthenticationException('Invalid credentials.');
    }
}

# security.yaml

security:
    firewalls:
        main:
            guard:
                authenticators:
                    - App\Security\EmailFormLoginAuthenticator