How to register changesets with rom config

The guide ROM - Framework setup mentions relations, commands, and mappers but nothing on changesets. I am currently using auto_registration with a namespace. I have tried a few things to no avail.

Where should I put this file to be picked up by auto register and avoid “uninitialized constant” error?

module RegisterNamespace
  module Changesets
    class CreateUserChangeset < ROM::Changeset::Create[:users]
      map do |tuple|

Changesets are not part of the auto registration. They will be in rom 6.0 though.

What is the method to manually register them?

There is no method because they aren’t yet registrable.