Upserts a contact using a speciifc identifier. If the contact exists it will be replaced, if not created.
*Note: If using the contactId as an identifier then if we cannot find the contact a 404 status code is returned instead of creating a contact, as you may not specify the contactId value!*
This call will be enabled in the unified contacts public preview as soon as possible. Remember you will need to have opted into the public preview in order to access this service.