Allows users to change language when not signed-in. thus, implementing proper language redirection as in Kolibri

[ozer550]

Summary

The Following Pr adds the functionality to the change language while viewing the public resources page or any other pages when not being signed in. It also implements proper redirection according to session and cookie data as in Kolibri.
closes #3150

Description of the change(s) you made

• Refactored set_language endpoint used for setting language
• Added a dropdown component with sign-in and change language option when the user is not signed in.
• Wrote tests to verify proper redirection.

Manual verification steps performed

1. Click on Explore without an account
2. Click on dropdown menu at top right.
3. Select a desired language.
4. open new tab (opens with selected language).

Screenshots (if applicable)

Before:

After:

Does this introduce any tech-debt items?

Reviewer guidance

How can a reviewer test these changes?

1. Click on Explore without an account from login page
2. Click on dropdown menu at top right.
3. Select a desired language.
4. open new tab (opens with selected language).

References

The set_language function is refactored from here

Contributor's Checklist

PR process:

Testing:

• Code is clean and well-commented
• 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
• Any new interactions have been added to the QA Sheet
• Critical and brittle code paths are covered by unit tests

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Reviewer's Checklist

This section is for reviewers to fill out.

• 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

[bjester]

In my testing, when I'm on the sign-in page and I change the language, the page refreshes again after reloading. It seems related to the service worker, and I think it must be the pwa/manifest.json causing it because it loads the language.

[bjester]

Looks good to me-- one comment about adding/updating the doc string

[bjester]

Could you add/replace the doc string here noting where this code came from and what you changed?