MSC3886: Simple client rendezvous capability

[hughns]

Rendered

• Servers:
  • [x] Standalone Rust server: https://github.com/matrix-org/rust-http-rendezvous-server
  • [x] Synapse homeserver module: https://pypi.org/project/matrix-http-rendezvous-synapse/
  • [x] Standalone prototype Node.js server: https://github.com/matrix-org/node-http-rendezvous-server
  • [x] Synapse experimental feature to delegate rendezvous to external server via an HTTP 307 redirect: https://github.com/matrix-org/synapse/pull/14018
• Clients:
  • [x] Element Web:
    • [x] matrix-js-sdk: https://github.com/matrix-org/matrix-js-sdk/pull/2747
    • [x] matrix-react-sdk: https://github.com/matrix-org/matrix-react-sdk/pull/9403
  • [x] Element iOS:
    • [x] https://github.com/vector-im/element-ios/pull/6806

[turt2live]

This was proposed as ready for FCP by the author, however it appears to have some conflicts with to-device messaging. For now, I'm going to put it into "needs technical design review". This doesn't mean it's not ready for FCP, just that the review's tone should take a slightly different shape.

@matrix-org/spec-core-team please review this for technical design.

[turt2live]

@hughns fyi that this has also entered "not active SCT focus" as it has a soft dependency on https://github.com/matrix-org/matrix-spec-proposals/pull/3906, which is also currently back with you.

When you get a chance to update the MSCs, we'll push 3906 forward at the same time as this one - just let us know in the SCT office.

[hughns]

It is proposed that MSC4108 supersedes this MSC.

[hughns]

Closing this PR as https://github.com/matrix-org/matrix-spec-proposals/pull/4108 is now ready for review.