Add a data transformer to transform a json to Author.

lib/decentralised_book_index/sync/data_transformers/author_transformer.ex

@@ -0,0 +1,14 @@
+defmodule DecentralisedBookIndex.Sync.DataTransformers.AuthorTransformer do
+
+  alias DecentralisedBookIndex.Metadata.Author
+
+  def from_json(json_body) do
+    author = %Author{
+      id: get_in(json_body, ["data", "id"]),
+      name: get_in(json_body, ["data", "attributes", "name"]),
+      description: get_in(json_body, ["data", "attributes", "description"]),
+    }
+
+    {:ok, author}
+  end
+end

test/decentralised_book_index/sync/data_transformers/author_transformer_test.exs

@@ -0,0 +1,33 @@
+defmodule DecentralisedBookIndex.Sync.DataTransformers.AuthorTransformerTest do
+  use ExUnit.Case, async: true
+
+  alias DecentralisedBookIndex.Sync.DataTransformers.AuthorTransformer
+  alias DecentralisedBookIndex.Metadata.Author
+
+  describe "correct transformations" do
+    test "a json contains correct author information" do
+      json_body = %{
+        "data" => %{
+          "attributes" => %{"description" => "Something", "name" => "Author"},
+          "id" => "889a323e-d104-4b5d-b276-dad5a9b1da9d",
+          "links" => %{},
+          "meta" => %{},
+          "relationships" => %{},
+          "type" => "author"
+        },
+        "jsonapi" => %{"version" => "1.0"},
+        "links" => %{
+          "self" => "http://localhost:4000/api/v1/json/author/889a323e-d104-4b5d-b276-dad5a9b1da9d"
+        },
+        "meta" => %{}
+      }
+
+      assert {:ok, author} = AuthorTransformer.from_json(json_body)
+      assert %Author{
+        id: "889a323e-d104-4b5d-b276-dad5a9b1da9d",
+        name: "Author",
+        description: "Something"
+      } = author
+    end
+  end
+end