POST /api/v2/conversations 405 when trying to set wrap-up code

We’ve got a script that auto-assigns wrap-up codes based on interaction duration. It works for updates, but I can’t figure out the endpoint for setting the final code after the call hangs up. I’m hitting POST /api/v2/conversations/{conversationId} with a simple payload, but it keeps coming back with a 405 Method Not Allowed. The docs are vague on post-interaction mutations.

Here’s the JSON I’m sending:

{
 "wrapup": {
 "code": "SOLD"
 }
}

What’s the correct endpoint to patch the wrap-up status?