Use case: as a cluster admin I want to be able to add  add custom configuration to an SMCP,  Istio resource, such as enable/disable kiali, access logs, and other Istio or OSSM components.  This story should also recommend the API details and:

• Whether to have a default ingress gateway (the "istio-ingressgateway" service).
• DNS (whether user should be able to disable automatic DNS records for Gateways).

(Replace all mention of SMCP with Istio resource in the rest of the description).

For Tech Preview, we haven't decided or designed a way for users to be able to add custom configuration to a SMCP when the cluster-ingress-operator is creating it. Currently, we hardcode a fixed configuration that would only support generic ingress use-cases.

https://issues.redhat.com/browse/NE-1178 says whether we can use an existing control plane and the outcome may influence the decision and design slightly, but this specific task is regarding when the cluster-ingress-operator is creating the SMCP (not integrating with an existing one). If you are able to integrate with an existing SMCP, then the ROI of this task is lessened (a workaround for customization is to make your own SMCP and then integrate with that). If NE-1178 outcome says you can't integrate with an existing SMCP, then this task may be more important (there's no workaround for custom configuration).

The outcome of this task should be a decision on what we are going to allow, the design (if we allow it), and an updated EP, specifically this open question regarding a new config object (which may be means by we allow custom configuration): https://github.com/openshift/enhancements/blob/master/enhancements/ingress/gateway-api-with-cluster-ingress-operator.md#do-we-need-a-new-config-object--how-can-the-cluster-admin-configure-ossm 

As a part of this effort, we should also consider metrics and if SMCP configuration options have any impact on getting metrics from Envoy.