Splitting an API post into models

I am building a Guest Registration and Management app that takes a form submission from a third party site. The form is complex and has potentially 80+ fields that cover a number of models in the app. I receive the data as json.

I’m unsure as to the best approach for taking this json and splitting it out to the various models (which are for reference; application, guest(s), patient, family, stay).

I’m considering a form object (of sorts) that takes the json payload and creates the models required, reporting back to the api controller.

Is this the best approach or is there a more conventional pattern?

Thanks in advance.