Enable multiple languages to be selected

[AdrianDAlessandro]

Description

This PR allows multiple languages in the Learning resources to be selected. This is necessary because the data contains this.

It does this using the django-multiselectfield package. Which requires a custom MultipleChoiceWidget to be made for the importing resources to work

Fixes #609

Type of change

• Documentation (non-breaking change that adds or improves the documentation)
• New feature (non-breaking change which adds functionality)
• Optimization (non-breaking, back-end change that speeds up the code)
• Technical work (non-breaking, change which is work as part of a new feature)
• Bug fix (non-breaking change which fixes an issue)
• Breaking change (whatever its nature)

Key checklist

• All tests pass (eg. python -m pytest)
• The documentation builds and looks OK (eg. mkdocs serve)
• Pre-commit hooks run successfully (eg. pre-commit run --all-files)

Further checks

• Code is commented, particularly in hard-to-understand areas
• Tests added or an issue has been opened to tackle that in the future. (Indicate issue here: # (issue))

[codecov]

Codecov Report

❌ Patch coverage is 95.65217% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
main/admin.py	80.00%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[Sahil590]

Overall LGTM. I had a few comments.
Would it be worth adding a check for empty values being passed? I know that the data will be reviewed before importing, but it may be missed.

[Sahil590]

The way it's rendered in the admin is through check boxes rather than the way a foreign key field is rendered so not the cleanest. I guess this will always be imported rather than be created manually?

[AdrianDAlessandro]

Yea, that's just the default for this multiselectfield. TBH I think the checkboxes are better than the default one that requires you to shift+click to highlight multiple.

This bit of code you've highlighted is for the list display, so that we can see the names of the languages in the table of all learning resources.

Would it be worth adding a check for empty values being passed? I know that the data will be reviewed before importing, but it may be missed.

It's already disallowing empty values for language, so the import will return an error for any empty ones

[Sahil590]

OK that's fine then. I thought there was something you could add in that file to render it differently. But this implementation works.