transformation.clj

 (def filters [{:data "DATA1"
                :name "NAME1"
                :users #{1 2 3}
                :url "URL1"
                :title "TITLE1"}
                {:data "DATA2"
                :name "NAME2"
                :users #{1 3}
                :url "URL2"
                :title "TITLE2"}])

(def magic-fn-output [{:user-id 1
                       :filters [{:data "DATA1"
                                  :name "NAME1"
                                  :users #{1 2 3}
                                  :url "URL1"
                                  :title "TITLE1"}
                                  {:data "DATA2"
                                  :name "NAME2"
                                  :users #{1 3}
                                  :url "URL2"
                                  :title "TITLE2"}]}
                       {:user-id 2
                        :filters [{:data "DATA1"
                                  :name "NAME1"
                                  :users #{1 2 3}
                                  :url "URL1"
                                  :title "TITLE1"}]}
                        {:user-id 3
                         :filters [{:data "DATA1"
                                  :name "NAME1"
                                  :users #{1 2 3}
                                  :url "URL1"
                                  :title "TITLE1"}
                                  {:data "DATA2"
                                  :name "NAME2"
                                  :users #{1 3}
                                  :url "URL2"
                                  :title "TITLE2"}])