Support MSC3779: "Owned" state events

[AndrewFerr]

See: MSC3779

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
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• Code style is correct
  (run the linters)

[erikjohnston]

Having read the MSC, I have serious reservations on it matrix-org/matrix-spec-proposals#3779 (comment). This doesn't necessarily block us from landing this as an experimental thing, but would block us from enabling it in non-test environments.

[erikjohnston]

From discussions elsewhere: we're looking at removing the changes to the required power levels, which is the controversial bit of the MSC. Until then, I'm going to remove this from the review queue.

[fkwp]

From discussions elsewhere: we're looking at removing the changes to the required power levels, which is the controversial bit of the MSC. Until then, I'm going to remove this from the review queue.

here we go #17513

[anoadragon453]

@AndrewFerr should this PR be closed in favour of #17513?

[AndrewFerr]

should this PR be closed in favour of #17513?

Sure. This is technically still a working implementation of an open MSC, but there's not much value in keeping this open alongside a competing PR & MSC.