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**Description**

Airflow 1.10 support providing a run_id to TriggerDagRunOperator using [DagRunOrder](https://github.com/apache/airflow/blob/v1-10-stable/airflow/operators/dagrun_operator.py#L30-L33) object that will be returned after calling [TriggerDagRunOperator#python_callable](https://github.com/apache/airflow/blob/v1-10-stable/airflow/operators/dagrun_operator.py#L88-L95). With https://github.com/apache/airflow/pull/6317 (Airflow 2.0), this behavior changed and one could not provide run_id anymore to the triggered dag, which is very odd to say the least.

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**Use case / motivation**

I want to be able to provide run_id for the TriggerDagRunOperator. In my case, I use the TriggerDagRunOperator to trigger 30K dag_run daily and will be so annoying to see them having unidentifiable run_id.

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After discussing with @ashb
**Suggested fixes can be**
 * provide a templated run_id as a parameter to TriggerDagRunOperator.
 * restore the old behavior of Airflow 1.10, where DagRunOrder holds the run_id and dag_run_conf of the triggered dag
 * create a new sub-class of TriggerDagRunOperator to fully customize it

**Are you willing to submit a PR?**

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**Related Issues**

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airflow/operators/trigger_dagrun.py
if not isinstance(execution_date, (str, datetime.datetime, type(None))):
            raise TypeError(
                "Expected str or datetime.datetime type for execution_date."
                "Got {}".format(type(execution_date))
            )
        self.execution_date: Optional[datetime.datetime] = execution_date  
        try:
            json.dumps(self.conf)
        except TypeError:
            raise AirflowException("conf parameter should be JSON Serializable")
    def execute(self, context: Dict):
        if isinstance(self.execution_date, datetime.datetime):
            execution_date = self.execution_date
        elif isinstance(self.execution_date, str):
            execution_date = timezone.parse(self.execution_date)
            self.execution_date = execution_date
        else:
            execution_date = timezone.utcnow()
        run_id = DagRun.generate_run_id(DagRunType.MANUAL, execution_date)
        try:
            
            
            dag_run = trigger_dag(
                dag_id=self.trigger_dag_id,
                run_id=run_id,
                conf=self.conf,
                execution_date=self.execution_date,
                replace_microseconds=False,
            )
        except DagRunAlreadyExists as e: