Envoy Overlay docs

[chandler-solo]

Description

This has lots of common elements with agentgateway/website#123

This work landed on main today in kgateway-dev/kgateway#13266

Change Type

/kind documentation

Changelog

NONE

Additional Notes

[chandler-solo]

Unstacked.

[chandler-solo]

Probably best to add env var examples:

Overlays will allow you to add/change/delete environment variables on envoy pods. It looks like the following:

spec:
  kube:
    deploymentOverlay:
      spec:
        template:
          spec:
            containers:
            - name: kgateway-proxy
              env:
              # Change existing ENVOY_UID to "1001"
              - name: ENVOY_UID
                value: "1001"
              # Add a new env var
              - name: CUSTOM_ENV
                value: custom-value
              # Delete existing POD_NAMESPACE
              - name: POD_NAMESPACE
                $patch: delete

[chandler-solo]

This should be revised to be more like agentgateway/website#142