[keycloak-user] Creating a user from a form different than the builtin registration form

I’m trying to understand what would be the best option to create a user for one of our realms from a marketing webpage that collects a lot of the user inputs. I realize we can customize the registration page through a theme, but in this particular case the marketing page collects a lot of additional information that feeds into other systems and one of the actions that we want to happen is create a user. Ideally we want to be able to do this on the client side since the page overall submits its info to different system that we do not control. Seems that if we can get our hands on the post URL that will be associated with the built-in registration page form, we can just do a POST to that, but we have not been able to find a good way to get that URL which includes a server side session_code parameter. Any pointers are much appreciated. Thanks, 0Georgi