Add ability to configure custom ports for experiment services that differ from ReplicaSet container ports.

[farid-akhoundov]

Summary

Hey Argo team!

I noticed when configuring A/B experiments that the port definitions for the generated services are set to use the same ones as on the ReplicaSet container, and I can't see any way to override this and specify custom ports. I was wondering if this is something to consider adding (or already on the team's radar)?

From what I can tell, the changes would need to be made here to override the value with those from the experiment TemplateSpec if they exist:

for _, ctr := range rs.Spec.Template.Spec.Containers {
    for _, port := range ctr.Ports {
	servicePort := corev1.ServicePort{
            Protocol:   port.Protocol,
            Port:       port.ContainerPort,
            TargetPort: intstr.FromInt(int(port.ContainerPort)),
	}
	if port.Name != "" {
            servicePort.Name = port.Name
	}
	ports = append(ports, servicePort)
    }
}

There was some discussion on doing this here, but it seems like the PR that resolved that issue may not have covered that specific use case. Also from what I can tell there's no strict requirement from Kubernetes for the service ports to match the ones on the ReplicaSet container.

Use Cases

Cases where the service ports should differ from the ones on the ReplicaSet container.

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