Update the AuthorTransformer to return a map instead of a struct.

lib/decentralised_book_index/sync/data_transformers/author_transformer.ex

@@ -3,7 +3,7 @@ defmodule DecentralisedBookIndex.Sync.DataTransformers.AuthorTransformer do
   alias DecentralisedBookIndex.Metadata.Author
 
   def from_json(json_body) do
-    author = %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"]),

test/decentralised_book_index/sync/data_transformers/author_transformer_test.exs

@@ -23,7 +23,7 @@ defmodule DecentralisedBookIndex.Sync.DataTransformers.AuthorTransformerTest do
       }
 
       assert {:ok, author} = AuthorTransformer.from_json(json_body)
-      assert %Author{
+      assert %{
         id: "889a323e-d104-4b5d-b276-dad5a9b1da9d",
         name: "Author",
         description: "Something"