Identify user based on custom parameter

Hi Team
We have an usecase wherer a Patient can add caregivers.On Adding caregiver event on UI we are hitting OKTA api from backend to create user without credential and send email api to send okta activation link on user mail to set the password.
we have an invitation table which stores invitation id(generated by our system for each caregiver) of caregiver user when we add in okta.
When user(caregiver) click on email activation link, he redirects to Okta Set password page and after password is set then okta is redirecting user to application
Here my doubt is I want to identify this user by its invitation id when he is redirected to application so that i can link this user with patient in backend

Can we add any custom parameter(key-value pair ex=“invitation_id”:“1234”) on Okta side at user level when we register user using Okta API?
Can we use this custom parameter(invitation_id) to be send by Okta after redirecting user to application?

@andrea please provide your input on this