Event-registration payments versus optional gifts

For GiveCampus integrations and API.

Yes, paid registration information belongs in the event-registration API: its payment object includes amount, currency, state, method, deposit and timestamps; attendee ticket types include price and fair market value. Optional event donations are separate contribution records, also referenced in registration donations with contribution ID and amount. Do not treat the registration payment itself as an everyday-giving contribution or double-count it with the optional donation. Guests use the same queued email-matching service as registrants, against school Individual records with unique identifiers. Guest constituent_id/constituent_ids are exposed under attendees, based on the base attendee identity. No email or no eligible imported match can leave IDs blank; multiple matching IDs are possible.