All `.Params` are stored lowercase, but it should work to access them `.Page.camelCase` etc. There was, however, some holes in the logic with the old transformer.
This commit fixes that by applying a blacklist instead of the old whitelist logic. `.Param` is a very distinct key. The original case will be kept in `.Data.Params.myParam`, but other than that it will be lowercased.
Fixes#5068