Create a new chat conversation and contact record for a phone number in the CRM.

Call this before sending a message to a new contact. If a chat already exists for this phone number on the same channel, a new record will still be created.

**Required steps before calling:**

1. Obtain a JWT via POST

2. Get your channelId from GET /api/wp-crm/channels/:orgIdReturns a chatId — use this in POST /api/wp-crm/messaging/send-message to send messages to this contact.