Make NotificationResultProcessor.emit wait until the batch is processed

[Johennes]

Content

This change makes NotificationResultProcessor own its lifecycle instead of relying on the push handler having been constructed first. emit starts the collector if it is not running, and results go through an unlimited channel, which holds items until a receiver takes them, so nothing is lost while the collector is starting or between it being launched and actually subscribing. emit also suspends until its batch has been processed, so the worker only completes once the notification or ringing call has been set up, and the wakelock or foreground service the worker holds covers the whole path rather than ending while the batch is still queued. Finally, a batch that throws while being processed is logged instead of cancelling the collector, which previously stopped all further notifications for the life of the process.

Motivation and context

NotificationResultProcessor currently hands resolved push events from the fetch worker to a collector running on the app scope. That collector is only started from DefaultPushHandler, which is only created when a push receiver runs in the current process, and the shared flow in between has no replay, so values emitted while nobody is subscribed are dropped. A FetchPendingNotificationsWorker that WorkManager runs in a fresh process, for example a retry after the process was killed or an expedited job that was deferred, therefore fetches and decrypts the events and then emits them into nothing. No notification is shown and nothing is logged.

Screenshots / GIFs

None.

Tests

See unit tests.

Tested devices

None.

Checklist

• I am aware of the etiquette.
• This PR was made with the help of AI:
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  • No.
• Changes have been tested on an Android device or Android emulator with API 24
• UI change has been tested on both light and dark themes
• Accessibility has been taken into account. See https://github.com/element-hq/element-x-android/blob/develop/CONTRIBUTING.md#accessibility
• Pull request is based on the develop branch
• Pull request title will be used in the release note, it clearly defines what will change for the user
• Pull request includes screenshots or videos if containing UI changes
• You've made a self review of your PR

[github-actions]

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[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 80.97%. Comparing base (67f287a) to head (14254b2).

Files with missing lines	Patch %	Lines
.../impl/notifications/NotificationResultProcessor.kt	94.44%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #7640      +/-   ##
===========================================
- Coverage    80.99%   80.97%   -0.02%     
===========================================
  Files         2781     2781              
  Lines        81847    81859      +12     
  Branches     11257    11258       +1     
===========================================
- Hits         66291    66288       -3     
- Misses       11211    11228      +17     
+ Partials      4345     4343       -2     

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