Content language setting is not working consistently in Skosmos 3

[osma]

URL address of the page where you encountered the problem

http://localhost/Skosmos/ykl/fi/

Description of the problem

1. Clear cookies for localhost (just in case)
2. Go to http://localhost/Skosmos/ykl/en/
3. In the content language dropdown, select Finnish (this will set the SKOSMOS_SEARCH_LANG cookie to fi and reload the page with the ?clang=fi attribute)
4. Again go to http://localhost/Skosmos/ykl/en/ (without the clang parameter)
5. Look at the content language selection: it shows Finnish, while the hierarchy shows class names in English.
6. Open one of the branches of the hierarchy (e.g. 0 GENERAL...)
7. The classes in the branch now have class names in Finnish

Additional information (e.g. screenshots) about the problem

I think the problem happens because of the way the SKOSMOS_SEARCH_LANG cookie is handled. The idea is to remember the content language chosen by the user. But in step 4 above, by the time the hierarchy renders, the SKOSMOS.content_language setting is still en and thus the top level of the hierarchy is rendered in English. When SKOSMOS.content_language is changed later by the search component, it's already too late, although subsequent request (for example opening new branches in step 6) will use the new setting.

Either we should drop the SKOSMOS_SEARCH_LANG cookie completely (it seems to me that having two mechanisms for this - the clang parameter and the cookie - is a recipe for problems) or if we need to keep it, then at least it should be processed very early in the frontend code (or possibly already on the backend side) so that SKOSMOS.content_language always matches the language set in the cookie.

The browser you used when the problem appeared

Firefox