**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/configuration.py
msg = (
                'Specifying both AIRFLOW_HOME environment variable and airflow_home '
                'in the config file is deprecated. Please use only the AIRFLOW_HOME '
                'environment variable and remove the config file entry.'
            )
            if 'AIRFLOW_HOME' in os.environ:
                warnings.warn(msg, category=DeprecationWarning)
            elif conf.get('core', 'airflow_home') == AIRFLOW_HOME:
                warnings.warn(
                    'Specifying airflow_home in the config file is deprecated. As you '
                    'have left it at the default value you should remove the setting '
                    'from your airflow.cfg and suffer no change in behaviour.',
                    category=DeprecationWarning,
                )
            else:
                AIRFLOW_HOME = conf.get('core', 'airflow_home')
                warnings.warn(msg, category=DeprecationWarning)
        
        
        if conf.getboolean('core', 'unit_test_mode'):
            conf.load_test_config()
    
    global WEBSERVER_CONFIG
    WEBSERVER_CONFIG = AIRFLOW_HOME + '/webserver_config.py'
    if not os.path.isfile(WEBSERVER_CONFIG):
        import shutil
        log.info('Creating new FAB webserver config file in: %s', WEBSERVER_CONFIG)
        shutil.copy(_default_config_file_path('default_webserver_config.py'), WEBSERVER_CONFIG)
    return conf
def load_test_config():