Function same_authority 

pub fn same_authority(a: &str, b: &str) -> bool

Whether a and b have the same authority, as a rule that only cares which server vouches for an identifier compares them: the same DID for portable identifiers, and for http and https ones the same host, whatever their schemes and ports, compared without regard to case. A portable identifier never has the authority of a web one, and an identifier that is neither has none.