**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
GRAPH_ENDPOINT = '/graph?dag_id={dag_id}'.format(
        dag_id=ViewWithDateTimeAndNumRunsAndDagRunsFormTester.DAG_ID
    )
    @classmethod
    def setUpClass(cls):
        super().setUpClass()
    def setUp(self):
        super().setUp()
        self.tester = ViewWithDateTimeAndNumRunsAndDagRunsFormTester(self, self.GRAPH_ENDPOINT)
        self.tester.setup()
    def tearDown(self):
        self.tester.teardown()
        super().tearDown()
    @classmethod
    def tearDownClass(cls):
        super().tearDownClass()
    def test_dt_nr_dr_form_default_parameters(self):
        self.tester.test_with_default_parameters()
    def test_dt_nr_dr_form_with_execution_date_parameter_only(self):
        self.tester.test_with_execution_date_parameter_only()
    def test_dt_nr_dr_form_with_base_date_and_num_runs_parameters_only(self):
        self.tester.test_with_base_date_and_num_runs_parameters_only()
    def test_dt_nr_dr_form_with_base_date_and_num_runs_and_execution_date_outside(self):
        self.tester.test_with_base_date_and_num_runs_and_execution_date_outside()
    def test_dt_nr_dr_form_with_base_date_and_num_runs_and_execution_date_within(self):
        self.tester.test_with_base_date_and_num_runs_and_execution_date_within()
class TestGanttView(TestBase):