Rewrite import and export subscriptions functionality using coroutines

[Isira-Seneviratne]

What is it?

• Bugfix (user facing)
• Feature (user facing)
• Codebase improvement (dev facing)
• Meta improvement to the project (dev facing)

Description of the changes in your PR

• Implement the subscription import/export functionality using CoroutineWorker for better performance and readability of the code.
• Make the import process cancellable (exporting usually completes too quickly to show a notification).
• Read/write subscription data using the Kotlinx Serialization library and plugin.
• Update WorkManager from 2.8.1 to 2.10.0 (changelog)
• Update the compile SDK to 35 (required by WorkManager).

Before/After Screenshots/Screen Record

Export

• Before:

Screen_recording_20241129_071419.webm

Android 6.0

• After:

Screen_recording_20241129_064527.webm

Android 6.0

Screen_recording_20241129_064829.mp4

Android 15

Fixes the following issue(s)

• Fixes #

APK testing

The APK can be found by going to the "Checks" tab below the title. On the left pane, click on "CI", scroll down to "artifacts" and click "app" to download the zip file which contains the debug APK of this PR. You can find more info and a video demonstration on this wiki page.

Due diligence

• I read the contribution guidelines.

[sonarcloud]

Quality Gate passed

Issues
6 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