Stabilize support for MSC3952: intentional mentions

[clokep]

Your use case

MSC3952 has been accepted, we should stabilize support for it by using the stable identifiers:

• org.matrix.msc3952.mentions -> m.mentions
• .org.matrix.msc3952.is_user_mention -> .m.rule.is_user_mention
• .org.matrix.msc3952.is_room_mention -> .m.rule.is_room_mention

And we should de-labs it after testing.

Have you considered any alternatives?

N/A

Additional context

See #25266 for a known bug in the implementation.

[clokep]

Also see matrix-org/synapse#15487 for stabilizing this in Synapse.

[clokep]

Note that this will be in the v1.7 release of the Matrix spec (if that needs to be checked).

[kerryarchibald]

Changes are drafted, will open for review following synapse changes and/or the EW user testing sessions.

[clokep]

@kerryarchibald I had a thought: should we update the buttons in the notification settings to disable the new push rules (in addition to the old)? Eg if you disable mentions it should probably toggle both versions?

Maybe this would be done with the settings UI rework though.

[kerryarchibald]

@clokep good thought! We should have that in place for the testing session. I'll make a ticket and coordinate with Janne

[Johennes]

Looks like the Synapse PR was merged. Is this ready to progress now?

[clokep]

It should be fine to, I think the element web code won't be used unless v1.7 is enabled in the server anyway? Not 100% sure how it is implemented.

[clokep]

@kerryarchibald Shall we close this or is it pending #25434?