**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
role_user = self.appbuilder.sm.find_role('User')
        self.appbuilder.sm.add_permission_role(role_user, read_perm_on_all_dag)
        self.appbuilder.sm.add_permission_role(role_user, edit_perm_on_all_dag)
        self.appbuilder.sm.add_permission_role(role_user, website_permission)
        read_only_perm_on_dag = self.appbuilder.sm.find_permission_view_menu(
            permissions.ACTION_CAN_READ, 'DAG:example_bash_operator'
        )
        dag_read_only_role = self.appbuilder.sm.find_role('dag_acl_read_only')
        self.appbuilder.sm.add_permission_role(dag_read_only_role, read_only_perm_on_dag)
        self.appbuilder.sm.add_permission_role(dag_read_only_role, website_permission)
    def test_permission_exist(self):
        self.create_user_and_login(
            username='permission_exist_user',
            role_name='permission_exist_role',
            perms=[
                (permissions.ACTION_CAN_READ, 'DAG:example_bash_operator'),
                (permissions.ACTION_CAN_EDIT, 'DAG:example_bash_operator'),
            ],
        )
        test_view_menu = self.appbuilder.sm.find_view_menu('DAG:example_bash_operator')
        perms_views = self.appbuilder.sm.find_permissions_view_menu(test_view_menu)
        self.assertEqual(len(perms_views), 2)
        perms = [str(perm) for perm in perms_views]
        expected_perms = [
            'can read on DAG:example_bash_operator',
            'can edit on DAG:example_bash_operator',
        ]
        for perm in expected_perms:
            self.assertIn(perm, perms)
    def test_role_permission_associate(self):