open threads via notification

[mahibi]

• more progress to resolve Message threads #3074

This PR will add the possibility to open threads via notification
(while keeping the behavior that backpress in thread that was opened via the threads-list should open the list again)

While it's tempting to do refactoring in the touched code parts, i won't do it now to avoid too many changes regarding the release of 22.0.0

Just some thoughts for later:

• is overriding handleOnBackPressed with own logic the best solution?

  • take a closer look at Jetpack's Navigation component
  • or should backstack regarding ChatActivity be handled via activity flags again (as intermediate solution if there will be more scenarios to consider?)?

• MainActivity might be removed in the future (redirecting could be done differently?, it only still exists as remnant from conductor architechture). This will also allow easier backstack handling (e.g. without the openedViaNotification solution in this PR, the old code

              if (isChatThread()) {
                  isEnabled = false
                  onBackPressedDispatcher.onBackPressed()
              } 
  

  ended up in showing the MainActivity (which should never be displayed besides when redirecting).

• NotificationWorker needs to be refactored. E.g. passing intents/bundles through the whole class is confusing...

🏁 Checklist

• ⛑️ Tests (unit and/or integration) are included or not needed
• 🔖 Capability is checked or not needed
• 🔙 Backport requests are created or not needed: /backport to stable-xx.x
• 📅 Milestone is set
• 🌸 PR title is meaningful (if it should be in the changelog: is it meaningful to users?)

[mahibi]

/backport to stable-22.0

[github-actions]

Codacy

Lint

Type	master	PR
Warnings	99	99
Errors	0	0

SpotBugs

Category	Base	New
Bad practice	6	6
Correctness	11	11
Dodgy code	62	62
Internationalization	3	3
Malicious code vulnerability	3	3
Performance	4	4
Security	1	1
Total	90	90

[github-actions]

APK file: https://www.kaminsky.me/nc-dev/android-artifacts/5395.apk



To test this change/fix you can simply download above APK file and install and test it in parallel to your existing Nextcloud app.