java: tipos incompatíveis

Revisei o código e esta conforme a aula, mas não consigo compilar o projeto por conta da class "AutenticacaoService"

package med.voll.api.domain.usuario;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.security.core.userdetails.UserDetails;
import org.springframework.security.core.userdetails.UserDetailsService;
import org.springframework.security.core.userdetails.UsernameNotFoundException;
import org.springframework.stereotype.Service;

@Service
public class AutenticacaoService implements UserDetailsService {

    @Autowired
    private UsuarioRepository repository;

    @Override
    public UserDetails loadUserByUsername(String username) throws UsernameNotFoundException{
        return repository.findById(username);
    }
}

Erro:

C:\Java\SpringBoot-Api_Rest\api\src\main\java\med\voll\api\domain\usuario\AutenticacaoService.java:17:36
java: incompatible types: java.lang.String cannot be converted to java.lang.Long

UsuarioRepository:

package med.voll.api.domain.usuario;

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.security.core.userdetails.UserDetails;

public interface UsuarioRepository extends JpaRepository<Usuario, Long> {
    UserDetails findByLogin(String login);
}

Quem puder me ajudar, obrigado.