Support rules inside traits

[plexus]

This doesn't seem to work at the moment.

(defactory customer-session
  {:state :OPEN}

  :traits
  {:redeemed
   {:with
    {:item_subsidies [{:sku rand-code}]
     :items [{:sku rand-code}]}
    :rules
    (let [?sku (facai/unify)]
      {[:item_subsidies :sku] ?sku
       [:items :sku] ?sku})}})