Store the default content type for an application.

    :param tornado.web.Application application: the application to modify
    :param str content_type: the content type to default to
    :param str|None encoding: encoding to use when one is unspecified

def set_default_content_type(application, content_type, encoding=None):
    """
    Store the default content type for an application.

    :param tornado.web.Application application: the application to modify
    :param str content_type: the content type to default to
    :param str|None encoding: encoding to use when one is unspecified

    """
    settings = get_settings(application, force_instance=True)
    settings.default_content_type = content_type
    settings.default_encoding = encoding