Allow control over transmitted language in HTTP requests

[Spruce8913]

Is your feature request related to a problem? Please describe.
Websites that open inside SEB can use the transmitted language header in the HTTP request to adapt their website. For example, GeoGebra, a calculator used all over the world and recently integrated somewhat better with SEB, translates its graphing commands based on the language in the HTTP-request.
HTTP requests send from SEB use the system language in the HTTP request, after this issue.

As GeoGebra (and other websites) are used all over the world, the system language of the student device does not always align with the preferred language header in the HTTP request. In any international study program (where students from another country take their own laptops with them), the system language will be most likely different (probably the students' native language) from the course language and thus in what language websites need to show up (probably English).

Describe the solution you'd like
A SEB-setting that allows separate control over "Accept-Language" language header in HTTP requests, and that defaults to "Use System Language".

Describe alternatives you've considered
Some websites allow control over the language with suffixes, for example https://www.wikiwand.com/en/search versus https://www.wikiwand.com/nl/search, but unfortunately not all of them...

In #549 where this was previously discussed, it is mentioned that "on maOS and iOS you can set the user interface language separately for specific apps. This then applies to UI and HTTP requests, but I wouldn't consider that an issue (why should the UI language of the browser be different than of the used assessment solution/web app). Don't know if Windows has such a per-app setting. [...for windows...] Unfortunately not, at least according to my knowledge, but some applications allow for command-line / startup arguments which can be saved in e.g. an application shortcut."

Though this is a functioning workaround on iOS and macOS, and some apps in Windows, it requires several technical steps, which is not always feasible in the field where there is limited IT-knowledge available.

Additional context
This feature request was mentioned in #549 about controlling the UI-language of SEB itself.

[dbuechel]

Thanks for the report, we'll definitely take it up in our backlog. But I unfortunately cannot promise anything with regard to the actual implementation; the prioritization and planning is done by our product owner board, of which I am not a part of.