exportTo needs to support label selectors

[NearchPasipou]

Describe the feature request

I need to exportTo resources to specific namespaces but without having to know those namespaces by name.

apiVersion: networking.istio.io/v1alpha3
kind: ServiceEntry
metadata:
  name: external-svc-httpbin
  namespace : egress
spec:
  hosts:
  - example.com
  exportTo: <--------------------
  - "."
  location: MESH_EXTERNAL
  ports:
  - number: 80
    name: http
    protocol: HTTP
  resolution: DNS

The issue is that this exportTo feature, as it seems, does not support label selectors.
So, while all namespaces with label:
mesh: enabled
belong to the service mesh / istio, there is no way to export resources to them unless I know all namespaces by name.

Which in my case is not possible since there are dynamically spawned preview environments (used for testing/developement) that each needs to join istio mesh and resides in a different namespace.

So, the use case here is, that I need to have resources exported in all istio enabled namespace and the name of all those istio enabled namespaces is not known beforehand.

I need to be able to exportTo the same way it is done with discovery selectors:

          discoverySelectors:
            - matchLabels:
                kubernetes.io/metadata.name: istio-system
            - matchLabels:
                mesh: enabled

Is something like this supported?
If not, shouldn't it be?

to make it more specific,

1. there are some resources that need to be exported only to istio-system namespace
2. some other resources that need to be exported to all those namespaces that are mesh enabled and I do not know their names beforehand (but NOT to be exported to the istio-system namespace)
3. some resources that need to be exported to all those namespaces that are mesh enabled and I do not know their names beforehand AND istio-system

[X] Networking
[X] Performance and Scalability
[X] User Experience

[ekarak-upwork]

+1

[hzxuzhonghu]

What is the sideeffect if you exportTo all namespaces for u? I think export to all istio managed namesapces equals to export to all namespaces, as for namespace not managed by istio, it has no effect at all