Spec for MSC2867 (Marking rooms as unread)

[Johennes]

Per MSC2867 (markdown)

Relates to: matrix-org/matrix-spec-proposals#2867
Signed-off-by: Johannes Marbach n0-0ne+github@mailbox.org

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[Johennes]

This currently generalizes the "Fully read markers" module to include read and unread markers because there are some shared semantics between these two. I'm curious if folks think this is a good idea. If not, the added subsections are easily moved to their own module.

Unlike for read markers, the MSC doesn't specify any API for unread markers. I assume this is because for unread markers there is no use case for performing any other actions (such as setting read receipts) simultaneously. Consequently, I haven't added any new CS endpoints here.

The MSC goes into quite a bit of detail around the UI treatment of unread rooms with red badges. I have interpreted this as an example and left the concrete UI treatment as an implementation detail in the spec.

[anoadragon453]

Just some minor wording tweaks, otherwise this LGTM!

This currently generalizes the "Fully read markers" module to include read and unread markers because there are some shared semantics between these two. I'm curious if folks think this is a good idea. If not, the added subsections are easily moved to their own module.

While you can easily implement one without the other, I think combining the two makes sense, as they are closely related concepts.

[anoadragon453]

Thank you!