enrich should be defined supporting both ds and db

[jleonard-r7]

Here is a suggested implementation:

(defn enrich [f]
  (->interceptor
   :id :rp-enrich
   :after (fn enrich-after [context]
            (let [event (get-coeffect context :event)
                  get-prev #(if (contains? (get-effect context) %1)
                              (get-effect context %1) ;; If no effect is returned, we provide the original coeffect.
                              (get-coeffect context %1))
                  prev-db (get-prev :db)
                  prev-ds (get-prev :ds)
                  new (f {:db prev-db :ds prev-ds} event)]
              (-> context
                  (assoc-effect :ds (or (:ds new) prev-ds))
                  (assoc-effect :db (or (:db new) prev-db)))))))