Function is_https_or_loopback 

pub fn is_https_or_loopback(url: &Url) -> bool

https, or plain http to loopback: the scheme rule for OAuth’s URLs (gateway spec §4, §5.7), which stays this even for a connection marked “internal network”, whose client check_url lets send plain http to internal addresses (plan 8b-ii). The OAuth caller checks it itself before sending (plan 8f).