Fix lesson visibility toggling for single user syncing

[rtibbles]

Summary

• Updates morango to prevent merge conflicts arising when deleted models are recreated
• Adds morango ecosystem tests to ensure that object recreation propagates, and that deletion propagation is still working as intended

References

Fixes #11208

Reviewer guidance

• Setup a learner only device from a server device
• On the server device toggle a lesson to be visible
• Let the sync to the learner only device happen
• Toggle the lesson to be invisible
• Let the sync to the learner only device happen
• Toggle the lesson to be visible again
• Let the sync to the learner only device happen

After each sync confirm the lesson is correctly displayed or not on the learner only device.

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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-0.16.0b6.dev0_git.56.g7f8896eb.pex
Windows Installer (EXE)	kolibri-0.16.0b6.dev0+git.56.g7f8896eb-unsigned.exe
Debian Package	kolibri_0.16.0b6.dev0+git.56.g7f8896eb-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.16.0b6.dev0+git.56.g7f8896eb-0.3.0.dmg
Android Package (APK)	kolibri-0.16.0b6.dev0+git.56.g7f8896eb-0.1.0-debug.apk
TAR file	kolibri-0.16.0b6.dev0+git.56.g7f8896eb.tar.gz
WHL file	kolibri-0.16.0b6.dev0+git.56.g7f8896eb-py2.py3-none-any.whl

[pcenov]

Hi @rtibbles, no issues observed with enabling/disabling the assigned lessons to a learner on a LOD.
Attaching the logs of the learn only device and the server in case you are able to spot anything wrong there:

LOD_logs.zip

Server_logs.zip

[jamalex]

Awesome, thank youuuu!