Only Kea (os-kea plugin) is supported — no active OPNsense environment
with legacy ISC DHCP was available to verify a second code path against.
Payload/response shapes (searchSubnet, searchReservation, addReservation,
setReservation, delReservation, service/reconfigure) were confirmed
against a real OPNsense box via a live add + verify + delete cycle
before writing this method and its tests.
Christian Manivong