> I believe some explicit configuration at the top of your Interactor implementation could go a long way here. Something 

I know I'm not a vote and just a voice. But boy, I really really dislike this approach. It's building on a ActiveRecord-like DSL for something can be simple.

I get `fail!("foo") unless context[:foo] == "foo"` is simpler than the DSL, but `context.fetch(:foo)` is a one liner that easily expresses what I'm trying to convey.