Function sign_in 

pub fn sign_in(
    account: Account,
    client_id: &str,
    authority: &Authority,
    taken: &[String],
    show: impl FnOnce(&str),
    stop: &AtomicBool,
) -> Result<Signed, SyncError>

Signs an address’s mail in with Microsoft, or signs it in again: Microsoft’s page (show opens it: the window’s browser, the terminal’s line), its answer, then the mailbox itself tried with the access given, before anything is kept (open_mailbox). account comes back at Microsoft’s servers, signed in with Microsoft, its sending server and its kind those the sign-in found. taken: the logins your other Microsoft accounts sign in as, refused here (the address before Microsoft’s page, the login it signed in after). A mailbox that opens only under another login than the address comes back with other_login, for the person’s Yes first; every sign-in ends with its answer (Signed::answer). When the mailbox does not open, nothing is kept.