add signature id

app/controllers/submit_form_values_controller.rb

@@ -15,7 +15,7 @@ class SubmitFormValuesController < ApplicationController
 
     render json: {
       value:,
-      attachment: attachment&.as_json(only: %i[uuid], methods: %i[url filename content_type])
+      attachment: attachment&.as_json(only: %i[uuid created_at], methods: %i[url filename content_type])
     }, head: :ok
   end
 end