Implement Third Party Lookups

[matrixbot]

This issue was originally created by @babolivier at https://github.com/matrix-org/dendrite/issues/633.

• [ ] Implement GET /_matrix/client/r0/thirdparty/protocols
• [ ] Implement GET /_matrix/client/r0/thirdparty/protocol/{protocol}
• [ ] Implement GET /_matrix/client/r0/thirdparty/location/{protocol}
• [ ] Implement GET /_matrix/client/r0/thirdparty/user/{protocol}
• [ ] Implement GET /_matrix/client/r0/thirdparty/location
• [ ] Implement GET /_matrix/client/r0/thirdparty/user

[matrixbot]

This comment was originally posted by @babolivier at https://github.com/matrix-org/dendrite/issues/633#issuecomment-452317695.

Actually there's a PR open for this: https://github.com/matrix-org/dendrite/pull/561

[matrixbot]

This comment was originally posted by @kegsay at https://github.com/matrix-org/dendrite/issues/633#issuecomment-679236775.

Sytests:

    × Can invite existing 3pid
    × Can invite existing 3pid with no ops into a private room
    × Can invite existing 3pid in createRoom
    × Can invite unbound 3pid
    × Can invite unbound 3pid over federation
    × Can invite unbound 3pid with no ops into a private room
    × Can invite unbound 3pid over federation with no ops into a private room
    × Can invite unbound 3pid over federation with users from both servers
    × Can accept unbound 3pid invite after inviter leaves
    × Can accept third party invite with /join
    × Can bind 3PID via home server
    × Can bind and unbind 3PID via homeserver
    × Can unbind 3PID via homeserver when bound out of band
    × 3PIDs are unbound after account deactivation
    × Can bind and unbind 3PID via /unbind by specifying the identity server
    × Can bind and unbind 3PID via /unbind without specifying the identity server

[matrixbot]

This comment was originally posted by @jittygitty at https://github.com/matrix-org/dendrite/issues/633#issuecomment-1140190252.

@spaetz Was that PR https://github.com/matrix-org/dendrite/pull/561 to address this deserted for any particular technical reason? I know its not "needed" to fix that Element Desktop app issue but was still wondering about #561