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**Description**

Related to the discussion here: https://github.com/apache/airflow/pull/8553#discussion_r416136954

Allow user to define expected terminal state. e.g. `JOB_STATE_CANCELLED` could be not treated as failure but expected terminal state.


<!-- A short description of your feature -->


self.gcp_conn_id = gcp_conn_id
        self.poll_sleep = poll_sleep
        self.impersonation_chain = impersonation_chain
        self.environment = environment
        self.cancel_timeout = cancel_timeout
        self.wait_until_finished = wait_until_finished
        self.append_job_name = append_job_name
        self.deferrable = deferrable
        self.job: dict | None = None
        self._validate_deferrable_params()
    def _validate_deferrable_params(self):
        if self.deferrable and self.wait_until_finished:
            raise ValueError(
                "Conflict between deferrable and wait_until_finished parameters "
                "because it makes operator as blocking when it requires to be deferred. "
                "It should be True as deferrable parameter or True as wait_until_finished."
            )
        if self.deferrable and self.wait_until_finished is None:
            self.wait_until_finished = False
    @cached_property
    def hook(self) -> DataflowHook:
        hook = DataflowHook(
            gcp_conn_id=self.gcp_conn_id,
            poll_sleep=self.poll_sleep,
            impersonation_chain=self.impersonation_chain,
            cancel_timeout=self.cancel_timeout,
            wait_until_finished=self.wait_until_finished,
        )
        return hook
    def execute(self, context: Context):