**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
from werkzeug.test import Client
from werkzeug.wrappers import BaseResponse
from airflow import models, settings, version
from airflow.config_templates.airflow_local_settings import DEFAULT_LOGGING_CONFIG
from airflow.configuration import conf
from airflow.executors.celery_executor import CeleryExecutor
from airflow.jobs.base_job import BaseJob
from airflow.models import DAG, Connection, DagRun, TaskInstance
from airflow.models.baseoperator import BaseOperator, BaseOperatorLink
from airflow.models.renderedtifields import RenderedTaskInstanceFields as RTIF
from airflow.models.serialized_dag import SerializedDagModel
from airflow.operators.bash import BashOperator
from airflow.operators.dummy import DummyOperator
from airflow.plugins_manager import AirflowPlugin, EntryPointSource
from airflow.security import permissions
from airflow.ti_deps.dependencies_states import QUEUEABLE_STATES, RUNNABLE_STATES
from airflow.utils import dates, timezone
from airflow.utils.log.logging_mixin import ExternalLoggingMixin
from airflow.utils.session import create_session
from airflow.utils.state import State
from airflow.utils.timezone import datetime
from airflow.utils.types import DagRunType
from airflow.www import app as application
from airflow.www.views import ConnectionModelView, get_safe_url
from tests.test_utils import fab_utils
from tests.test_utils.asserts import assert_queries_count
from tests.test_utils.config import conf_vars
from tests.test_utils.db import clear_db_runs
from tests.test_utils.mock_plugins import mock_plugin_manager
class TemplateWithContext(NamedTuple):