Function interpret 

pub fn interpret(response: &Response, registration: &Registration) -> Outcome

Read what a registrar said.

Takes the whole Registration rather than the two or three fields it happens to need today. A 2xx lists every binding for the address of record, so almost everything read out of one is read relative to what this client sent — its Contact to find its own row, its instance ID to find the GRUUs minted for it — and a signature that spells those out positionally grows a new argument every time the answer says something more.