One language call to rule them all

[allinox]

Description

A recent bug in profile (where 1/3 of all calls to it fails) revealed an issue with our current use of profile calls, namely that our BFF make calls to profile to get the user's language every time text with language support is required.
That means fetching every time a search in resources is performed, profile is called; for every search in api; every fetching of service owners for the filter; etc…

Instead of calling profile in three separate occasions on a single page to essentially get the same information, maybe we should instead reuse the language code fetched when the home controller is called. Especially since the change in language cannot be done from our pages at the moment and will not happen that frequently anyway. This will hopefully reduce vulnerability of errors like the current one in profile and also improve performance.

Consideration for language switching: In the future, when we implement an option to change language on our site we need to refetch localized data. Using language as part of the RTK cache key will automatically trigger this refetch.

Suggested solution:

• Make a global header that sets the user's language using the cookie value i18next (consider changing this name?) so that all calls to BFF contains this information in case it is needed for language support.
• Go through all BFF controllers and endpoints and make changes to use this new header value for language instead of fetching it from profile.