cubicweb #17050328 consider "ui.language" property in url-prefix mode [open]

If language-moe is set to url-prefix and no language prefix is used in the URL, CW uses language negotiation to set req's language.

If ui.site-title is specified, it should default to it otherwise we can't have set a default language for the UI.

prioritynormal
typebug
done in<not specified>
load0.250
load left0.250
closed by<not specified>