Dynamic / Optional segments with

[Obnotname]

On the SSR Framework I am using Dynamic or more precise in my case Optional segemts for multi-language support as follows

route(":lang?/settings", "./Settings.tsx")

It works great, however it of course routes everything not being a language to the settings module as well. So, example.com/not_a_language_/settings works as well.

Is there a way to specify specific supported languages and direct the rest to the 404 page, without having to do a runtime validation within the Settings.tsx module nor a specifying a route for each language separately?

😍 My preferred would be the following. Despite it doesn't have access to the supportededLngs variable:
route(":lang(de|fr|es)?/settings", "./Settings.tsx")

❌
route("de/settings", "./Settings.tsx")
route("fr/settings", "./Settings.tsx")
route("es/settings", "./Settings.tsx")

Finally, how is this handled by others, I assume simply by runtime validation within the module?