**Description**
In the trigger page, there is a text area to enter (optional) conf json. It would be great if a sample JSON can be provided programatically while defining DAG

**Use case / motivation**

This will improve usability of the UI that triggers a DAG

tests/www/test_views.py
dag = models.DagBag().get_dag("example_bash_operator")
        task0 = dag.get_task("runme_0")
        task1 = dag.get_task("runme_1")
        execution_date = datetime(2016, 1, 9)
        tis = [
            models.TaskInstance(task0, execution_date, state="success"),
            models.TaskInstance(task1, execution_date, state="failed"),
        ]
        self.session.bulk_save_objects(tis)
        dr = dag.create_dagrun(
            state="running",
            execution_date=execution_date,
            run_id="test_clear_dag_runs_action",
            session=self.session,
        )
        data = {"action": "clear", "rowid": [dr.id]}
        resp = self.client.post("/dagrun/action_post", data=data, follow_redirects=True)
        self.check_content_in_response("1 dag runs and 2 task instances were cleared", resp)
        self.assertEqual([ti.state for ti in self.session.query(models.TaskInstance).all()], [None, None])
    def test_clear_dag_runs_action_fails(self):
        data = {"action": "clear", "rowid": ["0"]}
        resp = self.client.post("/dagrun/action_post", data=data, follow_redirects=True)
        self.check_content_in_response("Failed to clear state", resp)
class TestDecorators(TestBase):