Flagger-managed `TraefikService` resources use the deprecated traefik.containo.us Kubernetes API group

[vytautaskubilius]

Describe the bug

The TraefikService resources that Flagger creates use the traefik.containo.us Kubernetes API group that has been deprecated in Traefik v3.

To Reproduce

1. Create a Flagger Canary resource that uses the traefik provider.
2. Upgrade Traefik to v3.
3. Observe the following errors in Traefik logs:

ERR error="the service \"default-podinfo-canary@kubernetescrd\" does not exist" entryPointName=web routerName=web-default-podinfo-canary-3dfb9b2aaefc944f017e@kubernetescrd

Looking at the TraefikService manifest that Flagger creates, it uses the traefik.containo.us Kubernetes API group that has been deprecated in the latest Traefik release:

apiVersion: traefik.containo.us/v1alpha1
kind: TraefikService
metadata:
  annotations:
    helm.toolkit.fluxcd.io/driftDetection: disabled
    kustomize.toolkit.fluxcd.io/reconcile: disabled
  creationTimestamp: "2023-10-25T13:18:14Z"
  generation: 60
  name: podinfo-canary
  namespace: default
  ownerReferences:
  - apiVersion: flagger.app/v1beta1
    blockOwnerDeletion: true
    controller: true
    kind: Canary
    name: podinfo-canary
    uid: d8071248-c040-4c39-861d-ac75bd6e6c05
  resourceVersion: "3271693529"
  uid: 6cae73fe-28c4-4c55-8aae-f7c58b65e487
spec:
  weighted:
    services:
    - name: podinfo-canary-primary
      namespace: default
      port: 80
      weight: 100

Expected behavior

Flagger creates TraefikService resources with the new traefik.io Kubernetes API group.

Additional context

• Flagger version: 1.37.0
• Kubernetes version: 1.27.11
• Service Mesh provider: N/A
• Ingress provider: Traefik