**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
"""Set state to 'up_for_retry'"""
        self.set_task_instance_state(tis, State.UP_FOR_RETRY)
        self.update_redirect()
        return redirect(self.get_redirect())
class DagModelView(AirflowModelView):
    """View to show records from DAG table"""
    route_base = '/dagmodel'
    datamodel = AirflowModelView.CustomSQLAInterface(DagModel)  
    class_permission_name = permissions.RESOURCE_DAG
    method_permission_name = {
        'list': 'read',
        'show': 'read',
    }
    base_permissions = [
        permissions.ACTION_CAN_READ,
        permissions.ACTION_CAN_EDIT,
        permissions.ACTION_CAN_DELETE,
    ]
    list_columns = [
        'dag_id',
        'is_paused',
        'last_scheduler_run',
        'last_expired',
        'scheduler_lock',
        'fileloc',
        'owners',
    ]
    formatters_columns = {'dag_id': wwwutils.dag_link}
    base_filters = [['dag_id', DagFilter, lambda: []]]
    def get_query(self):