verify-stack surfaced a Flowable 500: delivering messageEventReceived to the Beoordelen task's
execution is wrong — a message boundary event's subscription lives on its own execution. Correlate
instead by the registration's process instance id (recorded at submit): query the execution
subscribed to RegistratieIngetrokken and deliver the message there. Withdrawal moves from
IUserTaskClient to IWorkflowClient.WithdrawProcessAsync; the handler no longer needs a task lookup.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
