Function scout 

pub fn scout(
    address: &str,
    dav_host: Option<&str>,
    login: Option<(&str, &str)>,
) -> Scouted

What the server of address offers: its mail’s settings, a DAV server (dav_host when one is known already, else the domain’s), and a Nextcloud’s apps when login gives the password of the calendars at dav_host: it goes to that server only, never to another one found.