feat(calls): add support for sending Matrix RTC call notifications (MSC4075)

[stefanceriu]

This PR adds 2 new methods exposed all the way up to the ffi level that allow the client application to send call notifications when entering an Element call.

• send_call_notification_if_needed will check whether there's already an active call before chosing the notify type base don whether the room is a DM or not
• send_call_notification is supposed to be used for very custom use cases, logic living on the client
• it's also exposing a new CallNotify event type for the client to use when receiving a push notification
• part of MSC4075: MatrixRTC Call Ringing matrix-spec-proposals#4075
• powers Add support for showing the native OS incoming call screen when starting new Element Calls element-hq/element-x-ios#2862

NB I had a serious go at writing a test for this but setting it up is beyond my rust sdk knowledge. If you really think it's necessary please provide tips, tricks and send thoughts and prayers.

[codecov]

Codecov Report

Attention: Patch coverage is 93.33333% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 83.22%. Comparing base (d7a8877) to head (f5c8276).
Report is 18 commits behind head on main.

Files	Patch %	Lines
crates/matrix-sdk/src/room/mod.rs	93.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3434      +/-   ##
==========================================
- Coverage   83.23%   83.22%   -0.01%     
==========================================
  Files         247      247              
  Lines       25051    25066      +15     
==========================================
+ Hits        20851    20862      +11     
- Misses       4200     4204       +4     

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[andybalaam]

The code looks sensible to me but I have asked for help from other team members with more context since I'm not confident I understand the implications of this.

[andybalaam]

In terms of testing, it looks like you might be able to do it using a MockServer like test_cache_invalidation_while_encrypt does in crates/matrix-sdk/src/room/mod.rs

[andybalaam]

OK, no-one else who's around at the moment has much knowledge on the Element Call integration, so I've reviewed the code as best I can.

It looks good, but I would like it to be tested. Please could you give it a go? Feel free to ping me for a call to try and pair on it if it proves tricky.

[stefanceriu]

In terms of testing, it looks like you might be able to do it using a MockServer like test_cache_invalidation_while_encrypt does in crates/matrix-sdk/src/room/mod.rs

Thanks for the review. I already looked around but honestly all of this feels ridiculously complicated just to check a trivial piece of logic i.e. send a ring if it's a dm. Isn't there a simpler way to mock rooms in the rust sdk?

[andybalaam]

Thanks for the review. I already looked around but honestly all of this feels ridiculously complicated just to check a trivial piece of logic i.e. send a ring if it's a dm. Isn't there a simpler way to mock rooms in the rust sdk?

It does seem unfortunate that Room holds a concrete Client reference rather than some kind of trait object or type param. I'll ask the team in the room what they think.

[stefanceriu]

Alrighty, I managed to make something happen, please have another look

[andybalaam]

Looks great, thanks!

[jmartinesp]

I think someone from the Rust team has to hit the green button 😅 .