Previously, we were only returning a single ListenerPort for a single
service. However, we actually allow a single service to be serviced over
multiple ports, as well as allow users to define what hostnames they
expect their services to be contacted over. When no hosts are defined,
we return the default ingress domain for any configured DNS domain.
To show this in the UI, we modify the gateway-services-nodes API to
return a GatewayConfig.Addresses field, which is a list of addresses
over which the specific service can be contacted.
