Also mark the association as loaded

Author: Kyle d'Oliveira

lib/polymorphic_integer_type/extensions.rb

@@ -46,6 +46,7 @@ def belongs_to(name, scope = nil, **options)
             define_method "#{name}=" do |record|
               super(record)
               send("#{foreign_type}=", record.class)
+              association(name).loaded!
             end
           end