small fix for mapresponse

src/transformers/Transformer.js

@@ -57,7 +57,7 @@ function _mapResponse (response) {
         for (const key in include.relationships) {
           if (Object.hasOwnProperty.call(include.relationships, key) &&
           include.relationships[key].data && include.relationships[key].data.length > 0) {
-            obj.authors = _fetchIncludes({
+            obj[key] = _fetchIncludes({
               relation: include,
               response,
               type: key,