Create a migration guide for Gloo OSS Edge API users to move to kgateway API

[artberger]

• Edge to Kubernetes Gateway API changes (Gateway, GatewayClass, HTTPRoute, etc)
• Edge to kgateway API changes (RoutePolicy, ListenerPolicy, HttpListenerPolicy, DestinationRule, Backend)
  • apiVersion was gateway.gloo.solo.io/v1alpha1, but now is gateway.kgateway.dev/v1alpha1
  • policy selection, targetRefs to targetRef on the policies...but we might end up supporting this, check support targetRefs in policy attachment kgateway#10724
  • Backends (old upstreams) no longer can be automatically discovered --> need to confirm
  • No more Settings
  • HTTPListenerPolicy does not have options.healthcheck (used in AWS guide)
• install, ops, UX
  • no more glooctl
  • Helm chart is OCI, not http/https, so the Helm install flow is a little different
• resource naming differences
  • gloo-system to kgateway-system
  • gloo-proxy- prefix no longer added to the gateway proxies. Instead, it is just the proxy name, like http
• what happens to BYO things
  • external auth, TBD
  • access logging grpc server, we no longer have an example. Also can't BYO in the same way that you could in Edge

More resources:

• Slack request: https://cloud-native.slack.com/archives/C080D3PJMS4/p1740506963243089
• Another Slack about ext-auth: https://cloud-native.slack.com/archives/C080D3PJMS4/p1740512333210379
• Edge to K8s Gateway API guide: https://docs.solo.io/gateway/latest/installation/migrate-from-edge/