Declare support for Matrix v1.10

[clokep]

See matrix-org/synapse#16709 for a previous version of this.

See the changelog (note that I stripped out spec clarifications).

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Client-Server API

• Allow /versions to optionally accept authentication, as per MSC4026.
• Add local erasure requests, as per MSC4025.
  • This was essentially documenting what was implemented?
• Use the body field as optional media caption, as per MSC2530.
  • Client-only change.
• Add server support discovery endpoint, as per MSC1929.
• Add support for multi-stream VoIP, as per MSC3077.
  • Client-only change.
• Specify that the Retry-After header may be used to rate-limit a client, as per MSC4041.
  • Stabilize support for Retry-After header (MSC4014) #16947
• Add support for recursion on the GET /relations endpoints, as per MSC3981.
  • Stabliize support for MSC3981: recurse /relations #17023
• Clarify that the m.push_rules account data type cannot be set using the /account_data API, as per MSC4010.
  • Stabilize support for MSC4010: push rules & account data. #17022

[clokep]

@erikjohnston / @anoadragon453 I'd be curious on your thoughts on if Synapse could now declare v1.10 support:

• Auth for /versions should be accepted by Synape (but ignored) this seems inline with what the MSC proposes.
• Generally well-known endpoints aren't server by Synapse, and the server support endpoint isn't used by homeservers, so it is "supported".

🤷 Would be curious of opinions.

[anoadragon453]

* Auth for `/versions` _should_ be accepted by Synape (but ignored) this seems inline with what the MSC proposes.

I agree that we could call the current behaviour of Synapse, where it just ignores attempts at authenticating to /versions, "supporting" MSC4024.

* Generally well-known endpoints aren't server by Synapse, and the server support endpoint isn't used by homeservers, so it is "supported".

I agree that a "homeserver deployment" serving this endpoint via a separate webserver would thus constitute a full homeserver that supports Matrix v1.10. Synapse doesn't need to support serving this endpoint itself in order to declare support for v1.10.

I wouldn't be opposed to declaring v1.10 support before adding an option for Synapse to serve this endpoint itself.

[anoadragon453]

We discussed it briefly as the Element backend team and had no objections. So, go for it!