fix: first language visit

[johanseto]

Description

This fix is based in the method get_language_cookie default value. https://github.com/openedx/edx-platform/blob/master/openedx/core/djangoapps/lang_pref/helpers.py#L9

So in the first visit if the cookie doesnt exist, the language would be the configure by settings using LANGUAGE_CODE.If it is not defined, then would be None that is the default of the method.

Supporting information

Jira ticket:
https://edunext.atlassian.net/jira/software/c/projects/FUTUREX/boards/36?selectedIssue=FUTUREX-640

Testing instructions

Please provide detailed step-by-step instructions for testing this change.

[johanseto]

@andrey-canon I was trying to replicate this error in my local env and stage and I didn't reached out.
So I had to read the other middleware of dark_lang and I found that this language issues could be available if the clean-headers clean the header "HTTP_ACCEPT_LANGUAGE". If the model of dark lhas is configurable empty in released languages that header become ''.

And if that header is 'empty' then Django in the locale middleware uses the setting LANGUAGE_CODE value.
https://github.com/django/django/blob/main/django/middleware/locale.py#L34

Before

After

[OmarIthawi]

Thanks @johanv26. I believe you've spotted the right place.

If the model of dark lhas is configurable empty in released languages that header become ''.

I'm not sure if this is an option because DGA requires two languages with Arabic by default. We also might have sites that are English by default. What do you think?

So I had to read the other middleware of dark_lang and I found that this language issues could be available if the clean-headers clean the header "HTTP_ACCEPT_LANGUAGE".

I believe this is a good solution. Replacing HTTP_ACCEPT_LANGUAGE with settings.LANGUAGE_CODE is what we need, but only for non-API URLs because mobile would be Arabic-only otherwise.

I think lang_pref_helpers.get_language_cookie(request, getattr(settings, "LANGUAGE_CODE", None)) is better than dropping HTTP_ACCEPT_LANGUAGE because it affects only web.

As an optional refactoring note: My understanding that this is either should be an Open edX plugin by upgrading LocalizerX (Hawthorn) or putting it inside https://github.com/eduNEXT/eox-nelp but not in the eduNEXT/edunext-platform. But I'll leave that decision up to you.