post
https://api.qfp.quantnetwork.net/api/approvals/requests//cancel
The request becomes CANCELLED and every task still PENDING becomes
CANCELLED. Tasks already decided keep their outcome. resolvedBy is
the caller's sub. The resolution is published to policy.decided.
The request must be PENDING; anything else is a 409.
Any authenticated caller in the tenant may cancel. The check that
restricted this to the request's initiator is currently disabled.

