feat: Provide app-updated notifications for users

[susnux]

• Part of 📑 New in apps changelog display #9165

Summary

This provides information on what changed on an app update for users:
If notifications are enabled users will receive a notification for an app update if that app is enabled for that user.
The update notification is only provided if a changelog exists, to allow technical changelog and user changelogs following logic is applied:
As per appstore documentation CHANGELOG.md is used for technical changelogs (e.g. developers or administrators).
For users the CHANGELOG.{code}.md file is used ({code} is the language code), and it falls back to CHANGELOG.en.md if the requested language is missing.

Meaning: For user changelog CHANGELOG.{lang}.md with fallback CHANGELOG.en.md is used, for admins or developers use CHANGELOG.md.

Screen cast

vokoscreenNG-2024-03-03_18-34-33.mp4

TODO

• Add app config options to admin docs
• Would be nice to have unit tests.

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)