So this is about removing `_ITEM_TYPES` from `main.py`, correct?
I don't have a problem with that, as long as any relevant docs are updated and we're able to present a reasonable message when something goes wrong - either if there's a typo or the user executes a formula expecting type X with type Y (and therefore e.g. `koji_build` variable is required but not provided). It also means we should document the most commonly used types somewhere, so that people know for which events they can write their tasks and have them executed in our infra.