**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
"""
        Reads options, imports the full qualified name, and returns the object.
        In case of failure, it throws an exception with the key and section names
        :return: The object or None, if the option is empty
        """
        full_qualified_path = conf.get(section=section, key=key, **kwargs)
        if not full_qualified_path:
            return None
        try:
            return import_string(full_qualified_path)
        except ImportError as e:
            log.error(e)
            raise AirflowConfigException(
                f'The object could not be loaded. Please check "{key}" key in "{section}" section. '
                f'Current value: "{full_qualified_path}".'
            )
    def read(self, filenames, encoding=None):
        super().read(filenames=filenames, encoding=encoding)
    def read_dict(self, dictionary, source='<dict>'):
        super().read_dict(dictionary=dictionary, source=source)
    def has_option(self, section, option):
        try:
            
            
            
            self.get(section, option, fallback=_UNSET)
            return True
        except (NoOptionError, NoSectionError):
            return False
    def remove_option(self, section, option, remove_default=True):