demos/egress is a small Actor that fetches a URL it is given and echoes the
upstream status and body back, which makes the egress path observable from
outside the sandbox. hack/install-demo-egress.sh registers it as a
--deploy-demo-egress fixture and hack/verify-egress-demo.sh drives it and
checks the atenet-egress logs for the corresponding authorized CONNECT.
TestActorEgress in the networking suite covers the same path automatically:
it creates an Actor from the demo template, POSTs a fetch request through
atenet-router, and asserts 200. The suite's actor helper is parameterised by
template so the ingress test keeps using the counter fixture.