Fix LOD user management server sync interruptions

[LianaHarris360]

Summary

Previously when adding/removing users on the LOD, the syncing to the server would sometimes stop completely, with the error:

[python-devserver]   File "/Users/lianaharris/kolibri/kolibri/core/auth/tasks.py", line 450, in soud_sync_processing
[python-devserver]     execute_sync(Context(user_id, instance_id))
[python-devserver]   File "/Users/lianaharris/kolibri/kolibri/core/device/soud.py", line 389, in execute_sync
[python-devserver]     kwargs["facility"] = context.user.facility_id
[python-devserver]     raise self.model.DoesNotExist(
[python-devserver] kolibri.core.auth.models.FacilityUser.DoesNotExist: FacilityUser matching query does not exist.

Indicating that executing a sync for a user failed because the user did not exist. This occurred because, when an imported user was deleted, a server sync for that user was still queued. When the sync was executed, it failed, causing the syncing to stop. This issue has been resolved by removing the corresponding user SyncQueue object when deleting imported users.

• Remove users queued syncing tasks when deleting imported users
• Update DeleteImportedUserTestCase to have full database access to ensure the SyncQueue device model can be queried during testing

References

Fixes #13543

Reviewer guidance

1. On device 1 setup a server with learners
2. On device 2 setup a Learn-only device and import several learners
3. Start removing or adding learners for a period of time
4. The removed users syncing status on the full device should eventually say "Waiting to sync" and "Not recently synced"

[rtibbles]

Code changes make sense to me - and as we couldn't delete users from LoDs in 0.18 my first question of "Should we target this to the patch?" can be answered "No".

Just requires QA verification of the fix.

[AlexVelezLl]

Code changes make sense to me - and as we couldn't delete users from LoDs in 0.18 my first question of "Should we target this to the patch?" can be answered "No".

@rtibbles You mean removing the SyncQueue objects in the delete facility process too? This PR modifies the _get_user_related_models function that was introduced in 0.19, so we wouldn't be able to target the next 0.18 patch

[rtibbles]

Yes - my point was that because this is a bug in unreleased functionality, we wouldn't need to put this in a patch (I just wanted to get my thought down in Github in case anyone else wondered the same).

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.19.0a1.dev0_git.3.ga6ee98ee.pex
Windows Installer (EXE)	kolibri-0.19.0a1.dev0+git.3.ga6ee98ee-windows-setup-unsigned.exe
Debian Package	kolibri_0.19.0a1.dev0+git.3.ga6ee98ee-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.19.0a1.dev0+git.3.ga6ee98ee.dmg
Android Package (APK)	kolibri-0.19.0a1.dev0+git.3.ga6ee98ee-0.1.5-debug.apk
Raspberry Pi Image	kolibri-pi-image-0.19.0a1.dev0+git.3.ga6ee98ee.zip
TAR file	kolibri-0.19.0a1.dev0+git.3.ga6ee98ee.tar.gz
WHL file	kolibri-0.19.0a1.dev0+git.3.ga6ee98ee-py2.py3-none-any.whl

[rtibbles]

The Mac test failures here have been fixed in the release-v0.18.x branch, but have not yet been merged up to develop.

[pcenov]

Thanks @LianaHarris360, I confirm that the error is fixed now and syncing is functioning correctly.