Function resolve_auth 

pub(crate) fn resolve_auth(
    addr: SocketAddr,
    clustered: bool,
    tokens_file: Option<&Path>,
    session_key_file: Option<&Path>,
    insecure_no_auth: bool,
    cookie_secure: bool,
) -> Result<AuthState>

Decide the API authentication mode, refusing unsafe combinations before any side effects (#2, ADR-0010).