**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
"""
        This tests checks if Operator Link (AirflowLink2) defined in
        Airflow Plugin (AirflowLink2) is attached to all the list of
        operators defined in the AirflowLink2().operators property
        AirflowLink2 returns 'https://airflow.apache.org/1.10.5/' link
        GoogleLink returns 'https://www.google.com'
        """
        response = self.client.get(
            "{}?dag_id={}&task_id={}&execution_date={}&link_name=airflow".format(
                self.endpoint, self.dag.dag_id, self.task_2.task_id, self.default_date
            ),
            follow_redirects=True,
        )
        self.assertEqual(response.status_code, 200)
        response_str = response.data
        if isinstance(response.data, bytes):
            response_str = response_str.decode()
        self.assertEqual(
            json.loads(response_str), {'url': 'https://airflow.apache.org/1.10.5/', 'error': None}
        )
        response = self.client.get(
            "{}?dag_id={}&task_id={}&execution_date={}&link_name=airflow".format(
                self.endpoint, self.dag.dag_id, self.task_3.task_id, self.default_date
            ),