Update the FetchJsons to allow use a function to transform the data.

test/decentralised_book_index/sync/api_clients/fetch_jsons_test.exs

@@ -17,5 +17,21 @@ defmodule DecentralisedBookIndex.Sync.ApiClients.FetchJsonsTest do
       assert {:ok, records} = FetchJsons.get("#{@test_server_endpoint}/api/v1/json/author")
       assert length(records) == 11
     end
+
+    test "get authors names from API" do
+      for number <- 1..11 do
+        Metadata.create_author!("Author#{number}", "An description#{number}")
+      end
+
+      get_author_names = fn data ->
+        Enum.map(data, fn author -> author["attributes"]["name"] end)
+      end
+
+      assert {:ok, records} =
+        FetchJsons.get("#{@test_server_endpoint}/api/v1/json/author", get_author_names)
+
+      assert length(records) == 11
+      assert Enum.all?(records, fn author -> String.contains?(author, "Author") end)
+    end
   end
 end