tor-netdir: Add a by_id_pair() function to look up a relay by both IDs.

        Some(relay)

    }

    /// Return a relay matching a given Ed25519 identity and RSA identity,

    /// if we have a useable relay with _both_ keys.

    ///

    /// (Does not return unusable relays.)

    ///

    /// Note that if a microdescriptor is subsequently added for a relay

    /// with this ID, the ID may become usable.

    pub fn by_id_pair(&self, ed_id: &Ed25519Identity, rsa_id: &RsaIdentity) -> Option<Relay<'_>> {

        self.by_id(ed_id).filter(|r| r.rs.rsa_identity() == rsa_id)

    }

    /// Return a (possibly unusable) relay with a given RSA identity.

    #[allow(clippy::missing_panics_doc)] // Can't panic on valid object.

    fn by_rsa_id_unchecked(&self, rsa_id: &RsaIdentity) -> Option<UncheckedRelay<'_>> {

        let r = netdir.by_rsa_id_unchecked(&[13; 20].into()).unwrap();

        assert_eq!(r.rs.rsa_identity().as_bytes(), &[13; 20]);

        assert!(netdir.rsa_id_is_listed(&[13; 20].into()));

        use tor_linkspec::ChanTarget;

        let r = netdir.by_id_pair(&[13; 32].into(), &[13; 20].into());

        assert!(r.is_none());

        let r = netdir

            .by_id_pair(&[14; 32].into(), &[14; 20].into())

            .unwrap();

        assert_eq!(r.rsa_identity(), &[14; 20].into());

        assert_eq!(r.ed_identity(), &[14; 32].into());

    }

}