code: public function validateCredentials(Authenticatable $user, array $credentials)
      {
          return $this->ldap->auth(
              $user->dn,
              $credentials['password']
          );
      }
docs: Validate a user against the given credentials.
  
  @param  \Illuminate\Contracts\Auth\Authenticatable $user
  @param  array $credentials
  @return bool