refactor: process user connection event - WPB-10191

[jullianm]

WPB-10191 [iOS] Process UserConnectionEvent

Key points

This PR is part of the quick sync refactoring plan and is related to processing the multiple events we receive from the backend or the push channel.

Specifically, this PR is about porting the existing implementation of the UserConnection event.

When we receive an update connection event, the connection is updated locally.
if the connection is accepted, the processors tries to resolve the 1:1 conversation between a self user and another user depending on their common protocol (whether Proteus, MLS or no common protocol).

When the protocol is MLS, the processor tries to establish a new MLS group or join an existing group (depending on the epoch).

Testing

UTs cover the following use cases, ensuring that

• 1:1 conversation are properly resolved between a self user and another user (MLS, Proteus or no common protocol) by the processor
• connection is properly updated locally
• MLS 1:1 conversation is properly fetched from API
• MLS 1:1 conversation is properly pulled and stored locally.

Checklist

• Title contains a reference JIRA issue number like [WPB-XXX].
• Description is filled and free of optional paragraphs.
• Adds/updates automated tests.

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UI accessibility checklist

If your PR includes UI changes, please utilize this checklist:

• Make sure you use the API for UI elements that support large fonts.
• All colors are taken from WireDesign.ColorTheme or constructed using WireDesign.BaseColorPalette.
• New UI elements have Accessibility strings for VoiceOver.

[github-actions]

Test Results

2 603 tests   2 603 ✅  7m 0s ⏱️
  276 suites      0 💤
    3 files        0 ❌

Results for commit bb689f8.

♻️ This comment has been updated with latest results.

[johnxnguyen]

Nice work