apps/users: make switching the language via the indicator also change

[goapunk]

the users preferred language.

• add missing cookie settings to language cookie

fixes #2719

Tasks

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[m4ra]

@goapunk this fix has a side-effect that when we navigate the website and at some point switch to a language different from our preferences, when we navigate back to our account settings, then this new language becomes as our preferred (the language input becomes this chosen language we toggled). While currently whenever we navigate back to our account settings, it switches back to our default/preferred language. Is that ok @TeaJayyy?

[m4ra]

@goapunk did a quick demo to Tietje and the preferred language change is what should be expected, so am going to merge this.