Returns operations the registry declined, newest first. Filter on operation to
narrow to one kind.

This is wider than settlement. The registry declines credential offers and
service-onboarding requests through the same mechanism as transfers and issuance, so an
exception monitor that watches only transfer, mint and burn will silently miss
onboarding failures. operation enumerates the full set.

Each record carries the whole declined operation plus a reason. The field shape
is taken from the registry's own Daml templates and is therefore authoritative,
but reason is free text — the templates define no code vocabulary, so there
is nothing to branch on. Route on operation and surface reason to an operator.

Not every operation value necessarily has a corresponding rejection template in
the registry packages deployed on a given network. Filtering on an operation the
registry never produces a rejection for returns an empty page rather than an error.

This feed may be incomplete. The registry's reject choices write their rejection
record optionally, so an operation can be declined without a record appearing here.
A declined operation is always observable by its absence — the pending record closes
with no corresponding settlement or supply event — but the explicit rejection, and
therefore the reason, may not be captured.