What would you like to be added:

1. adding a new field under subGroupPolicy, a boolean flag to specific if service created automatically , the effect is kind of similar with subdomainPolicy: UniquePerReplica but this one is for "subGroups" instead of replica.
2. Create service if subGroup is specified and larger than 1.
3. Each service label-selector refers to leaderworkerset.sigs.k8s.io/subgroup-index: "{group-index}"
4. Service name looks like ${LwsInstanceName}-0-subgroup-$x

Do you think it's worthy of a KEP and code change ? @kannon92 @kerthcet @Edwinhr716

If yes, we can be assigned

Why is this needed:

Completion requirements:

This enhancement requires the following artifacts:

• Design doc
• API change
• Docs update

The artifacts should be linked in subsequent comments.