feat(push): add experimental support for MSC3768 (in-app-only notifications)

[Johennes]

This adds experimental support for MSC3768 by introducing the push rule action NotifyInApp and a room notification mode that is similar to mentions & keywords but notifies in-app rather than muting other notifications.

• [ ] Public API changes documented in changelogs (optional)

Signed-off-by:

[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 88.92%. Comparing base (92192c5) to head (c3a694c). :warning: Report is 49 commits behind head on main. :white_check_mark: All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5441   +/-   ##
=======================================
  Coverage   88.92%   88.92%           
=======================================
  Files         333      333           
  Lines       92267    92311   +44     
  Branches    92267    92311   +44     
=======================================
+ Hits        82051    82091   +40     
- Misses       6374     6378    +4     
  Partials     3842     3842           

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[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #5441 will not alter performance

_{Comparing Johennes:johannes/msc3768 (c3a694c) with main (872713c)}

Summary

✅ 31 untouched benchmarks

[Johennes]

For the tests, I'd like to integrate something into matrix-sdk-ui/tests/integration/notification_client.rs but I'm struggling a bit to see how to inject custom push rules in the client. It looks like all the current tests just run with the default push rules?

[Johennes]

Tests are still missing. I will need to figure out how to extend the existing ones.

[Johennes]

Moving back to draft to re-evaluate alternatives to MSC3768.