refactor: change lang selector logic

[dcoa]

Description and motivation

This PR refactors the lang selector logic recognizing its significance for multi-language instances.
The Open edX platform previously featured a configurable language selector in both the header and footer. However, after transitioning to microfrontends, this feature is only partially implemented in the footer. It requires passing a list of supported languages and a change function, necessitating additional modifications even when using the footer slot.

This PR change the dropdown and add the user preference update endpoint.

Proposal

Convert this component in a slot so could be installed in the header as well and give them the operators the option to use the language selector in the header or footer.

How to test

1. Override the Footer component in a MFE or use the example application to test the current implementation.
2. Add the configurations via env,config.js or MFE Config API.

const config = { ENABLE_FOOTER_LANG_SELECTOR: true, SITE_SUPPORTED_LANGUAGES: ['es', 'en'], };

3. You need the messages for the selected language if you want to visualize the change.
4. You can see the change in the language cookie.

2025-01-13.21-07-20.mov

[openedx-webhooks]

Thanks for the pull request, @dcoa!

This repository is currently unmaintained.

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 94.25%. Comparing base (bc79936) to head (7ec5478).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #493      +/-   ##
==========================================
+ Coverage   91.22%   94.25%   +3.02%     
==========================================
  Files           5        6       +1     
  Lines          57       87      +30     
  Branches       19       23       +4     
==========================================
+ Hits           52       82      +30     
  Misses          5        5              

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[dcoa]

Hi, @brian-smith-tcril I has wondering if you can have a look to this proposal or if should I tag someone from product before the technical review?

[brian-smith-tcril]

Sorry for the extended delay in response!

I think this is a change we do want. I also know that there is a similar feature implemented in frontend-base at the moment. Ideally the implementation of this feature will align with what is needed by the feature in frontend-base. I think @arbrandes has a better sense of what the frontend-base implementation is at the moment, and what we'll want it to be by the time we are ready to start using frontend-base.

Assuming this PR and the implementation in frontend-base play well together I'd be more than happy to review it!

[sarina]

should I tag someone from product before the technical review

I think there's a question of whether or not we want to be adding a new flag. If we don't mind a new flag this PR is good to go from a product perspective, but if we want to make this the default experience for any site that has multiple languages, you'd want to make a product ticket.

[dcoa]

@arbrandes I think your opinion here is valuable, understanding you have a better panorama of the current state of the frontend new architecture.

What do you think about this proposal and the alignment with frontend-base also the introduction of new config variables?