fix: Sending of message in empty MLS group #WPB-14747

[borichellow]

WPB-14747 [Android] Sending of messages in EMPTY MLS groups not working with latest 4.10 build

What's new in this PR?

Issues

When user creates empty MLS group (self user is the only member) and has only 1 client. Then sending messages always fails in such a group.

Causes (Optional)

According to logs, send message error: InvalidRequestError(errorResponse=ErrorResponse(code=400, message=Application messages at epoch 0 are not supported, label=mls-protocol-error, cause=null)).
Why epoch = 0?

How it should work: when client creates MLS group epoch set 0, after that we suppose to add some users and when do that epoch is updated. But when the group is empty, no updating epoch.
There is "workaround" for that case calling updateKeyingMaterial(idMapper.toCryptoModel(groupID)) but it didn't work because of if(userIdList.isEmpty()) but it's always false, cause userIdList includes self userId.

Solutions

Update if in internalAddMemberToMLSGroup to check not userIds but clientKeyPackageList if empty.
In that case when client creates empty MLS group clientKeyPackageList will be empty and workaround works.

[github-actions]

Test Results

3 340 tests  ±0   3 233 ✅ ±0   5m 52s ⏱️ +12s
  572 suites ±0     107 💤 ±0 
  572 files   ±0       0 ❌ ±0 

Results for commit 170c532. ± Comparison against base commit 6518915.

♻️ This comment has been updated with latest results.

[datadog-wireapp]

Datadog Report

Branch report: fix/sending_of_messages_in_empty_mls_group
Commit report: 788e969
Test service: kalium-jvm

✅ 0 Failed, 3233 Passed, 107 Skipped, 1m 2.4s Total Time

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 89.65517% with 3 lines in your changes missing coverage. Please review.

Project coverage is 54.14%. Comparing base (6518915) to head (170c532).

Files with missing lines	Patch %	Lines
...gic/data/conversation/MLSConversationRepository.kt	89.65%	3 Missing ⚠️

Additional details and impacted files

@@                  Coverage Diff                  @@
##           release/candidate    #3176      +/-   ##
=====================================================
- Coverage              54.14%   54.14%   -0.01%     
=====================================================
  Files                   1250     1250              
  Lines                  36457    36458       +1     
  Branches                3689     3689              
=====================================================
  Hits                   19739    19739              
- Misses                 15294    15295       +1     
  Partials                1424     1424              

Files with missing lines	Coverage Δ
...gic/data/conversation/MLSConversationRepository.kt	83.75% <89.65%> (+0.03%)	⬆️

... and 1 file with indirect coverage changes

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