Delegate RegistrationResponse#to_json to the params object

app/models/dor/registration_response.rb

@@ -1,15 +1,14 @@
 module Dor
   class RegistrationResponse
+    attr_reader :params
+    delegate :to_json, to: :params
+
     def initialize(p_hash)
       @params = p_hash
     end
 
     def to_txt
       @params[:pid]
     end
-
-    def to_json
-      @params.to_json
-    end
   end
 end

spec/controllers/objects_controller_spec.rb

@@ -25,7 +25,7 @@
     it 'registers the object with the registration service' do
       allow(Dor::RegistrationService).to receive(:create_from_request).and_return('pid' => 'druid:xyz')
 
-      post :create
+      post :create, format: :json
 
       expect(Dor::RegistrationService).to have_received(:create_from_request)
       expect(response.status).to eq(201)