Looks up the API URL for the given endpoint

    :param endpoint: The name of the registered route (aka endpoint)
    :type endpoint: string
    :returns: External URL for this endpoint
    :rtype: string/None

def url_for(endpoint, default=DEFAULT_ENDPOINT, **values):
    """Looks up the API URL for the given endpoint

    :param endpoint: The name of the registered route (aka endpoint)
    :type endpoint: string
    :returns: External URL for this endpoint
    :rtype: string/None
    """

    try:
        return router.url_for(endpoint, force_external=True, values=values)
    except Exception:
        logger.warn("Could not build API URL for endpoint '%s'. "
                    "No route provider registered?" % endpoint)
        # build generic API URL
        return router.url_for(default, force_external=True, values=values)