@Override
 public String checkLoginAndCalculateBasicAuth(UserDTO userDTO) {
   UserDTO user = findUserByEmailAndAlta(userDTO.getUsername());
   if (user != null) {
     if (passwordEncoder.matches(userDTO.getPassword(), user.getPassword())) {
       return PasswordUtils.calculateBasicAuth(user.getEmail(), userDTO.getPassword());
     }
   }
   return null;
 }