Function connect_and_auth

pub(crate) async fn connect_and_auth(
    context: &Context,
    proxy_config: &Option<ProxyConfig>,
    strict_tls: bool,
    candidate: ConnectionCandidate,
    oauth2: bool,
    addr: &str,
    user: &str,
    password: &str,
) -> Result<SmtpTransport<Box<dyn SessionBufStream>>>