RFC: Json Api Errors (WIP)

- ActiveModelSerializers::JsonPointer
- ActiveModel::Serializer::Adapter::JsonApi::Error
- ActiveModel::Serializer::Adapter::JsonApi::Error.attributes
- Fix rubocop config

lib/active_model/serializer/error_serializer.rb

@@ -0,0 +1,2 @@
+class ActiveModel::Serializer::ErrorSerializer < ActiveModel::Serializer
+end

lib/active_model/serializer/lint.rb

@@ -129,6 +129,20 @@ module ActiveModel::Serializer::Lint
       assert_instance_of resource_class.model_name, ActiveModel::Name
     end
 
+    def test_active_model_errors
+      assert_respond_to resource, :errors
+    end
+
+    def test_active_model_errors_human_attribute_name
+      assert_respond_to resource.class, :human_attribute_name
+      assert_equal(-2, resource.class.method(:human_attribute_name).arity)
+    end
+
+    def test_active_model_errors_lookup_ancestors
+      assert_respond_to resource.class, :lookup_ancestors
+      assert_equal 0, resource.class.method(:lookup_ancestors).arity
+    end
+
     private
 
     def resource