**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

airflow/www/views.py
"""Get rendered k8s yaml."""
        if not settings.IS_K8S_OR_K8SCELERY_EXECUTOR:
            abort(404)
        dag_id = request.args.get('dag_id')
        task_id = request.args.get('task_id')
        execution_date = request.args.get('execution_date')
        dttm = timezone.parse(execution_date)
        form = DateTimeForm(data={'execution_date': dttm})
        root = request.args.get('root', '')
        logging.info("Retrieving rendered templates.")
        dag = current_app.dag_bag.get_dag(dag_id)
        task = dag.get_task(task_id)
        ti = models.TaskInstance(task=task, execution_date=dttm)
        pod_spec = None
        try:
            pod_spec = ti.get_rendered_k8s_spec()
        except AirflowException as e:
            msg = "Error rendering Kubernetes POD Spec: " + escape(e)
            if e.__cause__:  
                msg += Markup("<br><br>OriginalError: ") + escape(e.__cause__)
            flash(msg, "error")
        except Exception as e:  
            flash("Error rendering Kubernetes Pod Spec: " + str(e), "error")