/oic/res is OCF's baseline resource-discovery endpoint: a unicast
RETRIEVE returns every href/Collection the connection hosts, not just
the one /device/0 seed path the coordinator polls. Relevant to the OCF
"Composite Device" model (issue #177) -- a single physical unit sharing
one IP/session across more than one logical Device, each exposed as its
own Collection resource (same rt shape as our own /device/0). Nothing
routes on this yet; captured alongside the existing /oic/p and /oic/d
reads so a report from a multi-unit device shows us whether its
firmware actually implements that model before any code assumes it does.