createContact adds a contact and can place it into segments or set per-topic
preferences in the same action.
automations/create-resend-contact.automation.ts
email is required. Optional fields are firstName, lastName, string-valued
properties, segments by exact name or ID, topic choices with opt_in or
opt_out, and global unsubscribed. Optional account selects the binding.
Segment names are resolved case-insensitively across all pages; missing or
ambiguous names fail. Returns { id: string; object: string }.