Configure NIC pods with `zone_sync` enabled without TLS support

[AlexFenlon]

Is your feature request related to a problem? Please describe.
As an engineer, I want zone_sync to a feature for NIC to allow state sharing.
Prereq: #7218

Acceptance Criteria

• No TLS for this issue
• zone-sync data read from the nginx-config (ConfigMap)
• input data validated
• generate headless service (no user input, read namespace name only)

headless service example:

apiVersion: v1
kind: Service
metadata:
  name: nginx-ingress-headless
  namespace: nginx-ingress
spec:
  clusterIP: None
  selector:
    app: nginx-ingress

-- lookup selector:app value from NIC deployment obj - it will be the name for app:selector in the headless service (we match NIC deployment with the headless service)
-- on NIC startup -> create headless service (K8s API call) - (?) Do we start NIC if this call fails?
-- learn where to put the code (controller.go ?) for managing config map zone-sync changes - during runtime
-- we need to remove headless service when user removes zone-sync (or set to false) from the nginx-ingress config map
-- we need to add headless service when user enables zone-sync (or set to true) in the nginx-ingress config map

• templates generate correct zone-sync config
• Manifest implementation
• Update Documentation
  • ready once this pr goes in

[github-actions]

Hi @AlexFenlon thanks for reporting!

Be sure to check out the docs and the Contributing Guidelines while you wait for a human to take a look at this 🙂

Cheers!