Django - 如何为注册网站用户和非网站用户提供模型？

I have a Trip model which can have many participants subscribed for a given trip and one owner. The participans are users registered on the site, but I also want to be able to add 'offline' users to the trip, users who do not have accounts on the site, so that I could keep track of all the users coming. The owner and participatns are linked to Userena user profile (side question: maybe linking directly to model which can have many partici