Fix `doctrine/annotations#create`

app/controllers/doctrine/annotations_controller.rb

@@ -6,7 +6,7 @@ class Doctrine::AnnotationsController < ApplicationController
     attrs = resource_params.to_unsafe_h
     document_id = attrs.delete(:document_id)
 
-    @annotation = Annotation.new(attrs)
+    @annotation = @doctrine.annotations.new(attrs)
 
     if document_id.present?
       @annotation.document = Cdao::Jurisprudence.find(attrs.delete(:document_id))