So you want something like `eitherContramap :: (b -> Either ErrMsg a) -> ValidationRule a -> ValidationRule b` we could define this as follows eitherContr

So you want something like `eitherContramap :: (b -> Either ErrMsg a) -> ValidationRule a -> ValidationRule b` we could define this as follows eitherContramap f rule = ValidationRule $ \b -> either failure (validate rule) (f b)