Refactor RegistrantUser class

* Extract frequently used country_code and ident methods
* Refactor domain query
* Add contact query method
* Add adminstrated_domains query method. Name will most likely change
  in the future developments
* Change registry locks integration test name

app/controllers/api/v1/registrant/base_controller.rb

@@ -39,7 +39,8 @@ module Api
           if decryptor.valid?
             sign_in decryptor.user
           else
-            render json: { errors: [{base: ['Not authorized']}] }, status: :unauthorized
+            render json: { errors: [{ base: ['Not authorized'] }] },
+                   status: :unauthorized
           end
         end