Upsert Intercom contacts, start conversations, and configure Fin AI agent handoff to human support via the Intercom REST API

Steps

1. Authenticate with a Bearer token from an Intercom app access token against https://api.intercom.io
2. POST /contacts with role:user or role:lead, email, name, and custom_attributes to create or upsert a contact — Intercom deduplicates by email for user role contacts
3. POST /conversations with the contact's id as from.id, from.type=user, and a body to initiate an outbound conversation or inject a message into an existing thread
4. Configure Fin AI agent in the Intercom UI to handle inbound conversations; use the Conversations API to set conversation_rating and tag conversations Fin could not resolve for agent review
5. To hand off from Fin to a human, assign the conversation via PATCH /conversations/{id}/parts with type:assignment, assignee_id (teammate or team ID), and body message
6. GET /conversations/{id} to verify assignment and retrieve the full conversation part history, including Fin's automated responses, for context handoff