entity map expansion

(require '[datomic.api :as d])

(def uri "datomic:mem://foo")
(d/create-database uri)
(def conn (d/connect uri))

@(d/transact conn [{:db/id (d/tempid :db.part/db)
                    :db/ident :card-1-reference
                    :db/valueType :db.type/ref
                    :db/isComponent true
                    :db/cardinality :db.cardinality/one
                    :db.install/_attribute :db.part/db}])

;; cardinality one nested map
@(d/transact conn [{:db/id (d/tempid :db.part/user)
                    :card-1-reference {:db/doc "nested entity map"}}])