**Description**

Enabled list of cors headers origin allowed

**Use case / motivation**

I'm currently developping Django application working with apache airflow for some external work through api. From Django, user run dag and a js request wait for dag end. By this way, I enabled cors headers in airflow.cfg with correct url. But now, I've  environment (dev & prod). It could be useful to be able to set more than one url in airflow.cfg cors header origin allowed

Thank's in advance :) 

airflow/www/extensions/init_views.py
)
    appbuilder.add_view(
        views.DagDependenciesView,
        permissions.RESOURCE_DAG_DEPENDENCIES,
        category=permissions.RESOURCE_BROWSE_MENU,
    )
    
    
    appbuilder.add_view_no_menu(views.RedocView)
def init_plugins(app):
    """Integrate Flask and FAB with plugins"""
    from airflow import plugins_manager
    plugins_manager.initialize_web_ui_plugins()
    appbuilder = app.appbuilder
    for view in plugins_manager.flask_appbuilder_views:
        name = view.get('name')
        if name:
            log.debug("Adding view %s with menu", name)
            appbuilder.add_view(view["view"], name, category=view["category"])
        else:
            
            log.debug("Adding view %s without menu", str(type(view["view"])))
            appbuilder.add_view_no_menu(view["view"])
    for menu_link in sorted(plugins_manager.flask_appbuilder_menu_links, key=lambda x: x["name"]):
        log.debug("Adding menu link %s to %s", menu_link["name"], menu_link["href"])
        appbuilder.add_link(**menu_link)
    for blue_print in plugins_manager.flask_blueprints:
        log.debug("Adding blueprint %s:%s", blue_print["name"], blue_print["blueprint"].import_name)
        app.register_blueprint(blue_print["blueprint"])
def init_connection_form():