title: How to capture passed --conf parameter in called DAG in Airflow
body: <p>I am trying to run a DAG from REST API and pass some parameters to it. The DAG should be able to catch the parameters and use it. The problem is I am able to trigger the DAG from REST API,but the DAG is not able to catch the parameters passed. Is there a way to achieve this?</p>
  
  <p>I am triggering the DAG from REST API as below.It passes the parameters in --conf</p>
  
  <pre><code>http://abcairflow.com:8090/admin/rest_api/api?api=trigger_dag\&amp;dag_id=trigger_test_dag\&amp;conf=%7B%22key%22%3A%2
  </code></pre>
  
  <p>How to capture the values passed in conf value in the called DAG. As far as I know the conf should take the URL encoded JSON format data.</p>
  
  <p>DAG code:`</p>
  
  <pre><code>def run_this_func(**kwargs):
  print(kwargs)
  
  run_this = PythonOperator(
      task_id='run_this',
      python_callable=run_this_func,
      dag=dag
  )`
  </code></pre>