Return errors in API playlists/create

app/controllers/api/playlists_controller.rb

@@ -14,7 +14,7 @@ module API
       if @playlist.save
         render :show, status: :created
       else
-        render json: :nothing, status: :unprocessable_entity
+        render json: @playlist.errors, status: :unprocessable_entity
       end
     end
 

spec/integration/api/playlists_spec.rb

@@ -47,6 +47,12 @@ describe 'API playlists' do
       it 'responds with unprocessable entity status' do
         expect(response).to have_http_status 422
       end
+
+      it 'returns errors' do
+        expect(json 422).to match(
+          name: [an_instance_of(String)]
+        )
+      end
     end
   end