Fix learner sync status reporting on server device

[rtibbles]

Summary

• Ensures that we always return a non-null sync status
• This should show up in the frontend as a sync being shown as 'not recently synced' - additional fixes are needed in Morango to ensure that the sync session gets properly attached to the user sync status.
• Fixes the check for whether we have a local context, which previously was always erroneously early returning.
• Combined with Ensure initialization signals get fired during sync morango#201 this fixes the setting of learner sync status sync session foreign keys

References

Fixes #10588

Reviewer guidance

Do tests pass? Does the new test cover the scenario of a sync session not being assigned to the status?

Use the morango code in the linked PR and do pip install -e <path to morango repo> to do a full manual test of this.

Install an LOD learner from a server running this PR, and once it has synced, the sync status should properly display.

See screenshot of the active sync updating properly:

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Testing checklist

• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Critical and brittle code paths are covered by unit tests

PR process

• PR has the correct target branch and milestone
• PR has 'needs review' or 'work-in-progress' label
• If PR is ready for review, a reviewer has been added. (Don't use 'Assignees')
• If this is an important user-facing change, PR or related issue has a 'changelog' label
• If this includes an internal dependency change, a link to the diff is provided

Reviewer checklist

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[github-actions]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.16.0b5.dev0_git.134.gf6b860e3.pex
Windows Installer (EXE)	kolibri-0.16.0b5.dev0+git.134.gf6b860e3-unsigned.exe
Debian Package	kolibri_0.16.0b5.dev0+git.134.gf6b860e3-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0b5.dev0+git.134.gf6b860e3-0.3.0.dmg
Android Package (APK)	kolibri-0.16.0b5.dev0+git.134.gf6b860e3-0.1.0-debug.apk
TAR file	kolibri-0.16.0b5.dev0+git.134.gf6b860e3.tar.gz
WHL file	kolibri-0.16.0b5.dev0+git.134.gf6b860e3-py2.py3-none-any.whl

[jredrejo]

Code makes sense. I only miss a case in test_sync_event_hook_utils.py to test with local_context set to None.

In any case, tested it and it works perfectly using the morango PR code:

[rtibbles]

Thanks @jredrejo - I thought of adding that test case just after I signed off last night, so glad to have my thought validated. I'll add one now!

[rtibbles]

Note, it's possible that this PR will also fix this issue: #11234