**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
task_dict['state'] = State.FAILED
            task_dict['operator'] = task.task_type
            task_dict['try_number'] = try_count
            task_dict['extraLinks'] = task.extra_links
            tasks.append(task_dict)
        data = {
            'taskNames': [ti.task_id for ti in tis],
            'tasks': tasks,
            'height': len(tis) * 25 + 25,
        }
        session.commit()
        return self.render_template(
            'airflow/gantt.html',
            dag=dag,
            execution_date=dttm.isoformat(),
            form=form,
            data=data,
            base_date='',
            demo_mode=demo_mode,
            root=root,
        )
    @expose('/extra_links')
    @auth.has_access(
        [
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_DAG),
            (permissions.ACTION_CAN_READ, permissions.RESOURCE_TASK_INSTANCE),
        ]
    )
    @action_logging
    def extra_links(self):