Submit wallet signatures and create or change the user’s Polymarket username.
POST /v3/polymarket/profiles/username/complete
Completes a previously created username challenge. This endpoint consumes the challenge atomically, verifies both wallet signatures, logs in to Polymarket, creates the profile if needed, and sets the username.
Call this from your backend with the same PolyNode API key that created the challenge. Do not call it directly from the browser.