**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
template: jinja2.environment.Template
    context: Dict[str, Any]
    @property
    def name(self):
        return self.template.name
    @property
    def local_context(self):
        """Returns context without global arguments"""
        result = copy.copy(self.context)
        keys_to_delete = [
            
            'g',
            'request',
            'session',
            
            'csrf_token',
            
            'current_user',
            
            'appbuilder',
            'base_template',
            
            'server_timezone',
            'default_ui_timezone',
            'hostname',
            'navbar_color',
            'log_fetch_delay_sec',
            'log_auto_tailing_offset',
            'log_animation_speed',