Support editing Endpoint Slice #848

Hello,

I just want to say you've written an amazing application and my team has swapped to using it full time as it honestly blows other solutions out of the water.

Problem statement

Currently Radar doesn't support EndpointSlice, so if someone has created a service with manual resolution via EndpointSlice they are unable to edit/view this information.

https://kubernetes.io/docs/reference/kubernetes-api/discovery/endpoint-slice-v1/

One use case we have here is we have an external dialing system, where we create a service that allows our internal Kubernetes services to call these external diallers without each service needing to know their IPs as they can just reference this internal service name.

apiVersion: v1
kind: Service
metadata:
  name: dial-lb
  namespace: external
spec:
  type: ClusterIP
  ports:
    - name: http
      port: 80
      targetPort: 80
---
apiVersion: discovery.k8s.io/v1
kind: EndpointSlice
metadata:
  name: dial-lb-slice
  namespace: external
  labels:
    kubernetes.io/service-name: dial-lb
addressType: IPv4
ports:
  - name: http
    appProtocol: http
    port: 80
endpoints:
  - addresses:
      - 10.9.0.43
      - 10.9.0.44
      - 10.9.0.45
      - 10.9.0.46
      - 10.9.0.47
      - 10.9.0.48
    conditions:
      ready: true
      serving: true

Its a fairly niche use case but it is handy.