Fix creating a quiz without having imported resources or users enrolled in the class

[AllanOXDi]

Summary

This pull request adds warning messages for scenarios in which there are no imported channels and/or users associated with the class when a coach attempts to create a quiz.

References

#12330

Reviewer guidance

1. Please review the slack conversations for some decisions made whether to use a model or not here and here
2. Does the changes makes sense ?

Testing checklist

• [x] 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

• 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[bot]]

Build Artifacts

Asset type	Download link
PEX file	kolibri-0.18.0.dev0_git.20241106004307.pex
Windows Installer (EXE)	kolibri-0.18.0.dev0+git.20241106004307-windows-setup-unsigned.exe
Debian Package	kolibri_0.18.0.dev0+git.20241106004307-0ubuntu1_all.deb
Mac Installer (DMG)	kolibri-0.18.0.dev0+git.20241106004307.dmg
Android Package (APK)	kolibri-0.18.0.dev0+git.20241106004307-0.1.4-debug.apk
TAR file	kolibri-0.18.0.dev0+git.20241106004307.tar.gz
WHL file	kolibri-0.18.0.dev0+git.20241106004307-py2.py3-none-any.whl

[marcellamaki]

Hi @AllanOXDi - this is ready to go, but can you please remove the yarn.lock file as it is not related to this changes? Then we can merge