Topic: Where to place constraint classes?

Hi,

in my routes.rb I have somesting like:

match ":kreis", :constraints => ConstraintKreis.new, :to => redirect("/%{kreis}/start")

If I place the class ConstraintKreis directly into the routes.rb, everything works fine. But I would prefer to have that class in a separate file. Where (directory and file name) do I have to place that file?

Thanks