Use cases:

1. As a customer I would like to understand how and when DNS records are created for my Gateway API resources.
2. As a developer I would like to fix any issues that are not acceptable, or document those that cannot be resolved.

See

Enhancement Proposal - new controller to manage dns records for gateway listeners

and https://github.com/openshift/cluster-ingress-operator/blob/master/pkg/operator/controller/gateway-service-dns/controller.go#L159 

Write and run unit test cases to find answers to the following about the current Gateway API DNS reconciliation:

1. Does it work with multiple Gateways?  Create multiple Gateways that have listeners with same hostname, as well as with differing hostnames and test DNS flow.
2. What happens for a Gateway with Listeners that don't have a hostname?
3. Does it ignore Services that are not associated with the Gateway controller?
4. Other important factors TBD.

Acceptance Criteria: new unit test cases, documentation, and update to enhancement document if needed.