Log in with PayPal status
Polls the outcome of a Log in with PayPal attempt for the authenticated
withdrawer. The widget calls this while its popup is open; the server-side
return handler links the account and records linked/error on the
session, so completion never relies on the popup messaging the widget.
Authentication
Query parameters
Response
States of a single Log in with PayPal attempt. cancelled is a distinct
terminal state for when the withdrawer declines consent on PayPal (no code to
exchange) — the widget returns quietly to the methods screen rather than
showing a linking-failed error.

