**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
application.app = None
        application.appbuilder = None
        app = application.cached_app(config={'WTF_CSRF_ENABLED': False}, testing=True)
        cls.client = Client(app, BaseResponse)
    @classmethod
    def tearDownClass(cls):
        application.app = None
        application.appbuilder = None
    def test_mount(self):
        
        resp = self.client.get('/test/health')
        self.assertEqual(resp.status_code, 200)
        self.assertIn(b"healthy", resp.data)
    def test_not_found(self):
        resp = self.client.get('/', follow_redirects=True)
        self.assertEqual(resp.status_code, 404)
    def test_index(self):
        resp = self.client.get('/test/')
        self.assertEqual(resp.status_code, 302)
        self.assertEqual(resp.headers['Location'], 'http://localhost/test/home')
class TestAirflowBaseViews(TestBase):
    EXAMPLE_DAG_DEFAULT_DATE = dates.days_ago(2)
    @classmethod
    def setUpClass(cls):
        super().setUpClass()
        models.DagBag(include_examples=True).sync_to_db()
        cls.dagbag = models.DagBag(include_examples=True, read_dags_from_db=True)
        cls.app.dag_bag = cls.dagbag
    def setUp(self):