Registration Callback URL - OIDC

I have successfully configured the OIDC and is working as expected. Then I configured the ‘registration_callback_url’ which is in my case a Node-RED instance. I see the post request comming, which includes the ‘user_id’. Now, the only thing I can do is to create eg. a new organization for users which are not yet registered. But how could I implement a fuctionality to automatically onboard e.g. an administration user or add a new user to a specific organization? Isn’t there a posibillity to add more information to this POST request, e.g. like group or other metadata comming from the OIDC provider?
Would like to here what others think about that…