Returns the thread ID for an existing DM conversation with the given platform user. Returns 404 if no prior conversation exists with that user. Use the returned thread_id to send messages via POST /accounts/:id/dms/:tid/send. Requires Starter plan or higher.
Prefix your API key with "Bearer ". Example: Authorization: Bearer soc_live_...
Connected account ID
Platform-specific user ID to look up
Thread ID for the existing conversation
"t_17841405793187218"