通过密码检查身份

async def check_passwd(self, 
        identity: str, 
        passwd: str
    ) -> SessionIdentity :
        """ 通过密码检查身份 """
        assert identity

        value, _ = await self._client.get(f"{self._prefix_identity}/{identity}")
        if value is None:
            logger.debug(f'Not found identity: {identity}')
            raise Unauthorized(f"无此登录身份'{identity}'")

        profile = json.loads(value.decode('utf-8'))

        user_id = profile['user_id']
        identity = profile['identity']
        hashed = profile['hashed']

        if sha256_crypt.verify(passwd, hashed):
            return SessionIdentity(user_id=user_id, identity=identity)
        else:
            raise Unauthorized(f"登录身份'{identity}'认证失败")