Add support for multiple ArgoCD servers.

[sl1pm4t]

Some folks deploy an ArgoCD server per Kubernetes cluster. We should add support for multiple ArgoCD deploys that is configurable:

• per repository
• per application

[Oded-B]

Hi, I'm the author of https://github.com/wayfair-incubator/telefonistka, I used this configuration format to support forwarding webhook to arbitrary number of ArgoCDs:
I think a similar configuration could be used.

webhookEndpointRegexs:
  - expression: "^workspace/[^/]*/.*"
    replacements:
      - "https://kube-argocd-c1.service.lab.example.com/api/webhoook"
      - "https://kube-argocd-applicationset-c1.service.lab.example.com/api/webhoook"
      - "https://example.com"
  - expression: "^clusters/([^/]*)/([^/]*)/([^/]*)/.*"
    replacements:
      - "https://kube-argocd-${3}.${1}.service.{2}.example.com/api/webhoook"
      - "https://kube-argocd-applicationset-${2}.service.${1}.example.com/api/webhoook"

For authentication, I would use Dex OIDC connector on server side and have Kubechecks use Dex token exchange to replace the in-pod k8s SA JWT (/var/run/secrets/kubernetes.io/serviceaccount/X) with an ArgoCD valid access token.

BTW I'm half way in implementing "post argocd diff in PR comment" in Telefonistka and just ran in to your amazing project.
I'm considering just using kubechecks, but I'm not sure it will be fully compatible to my future plans

[Greyeye]

few changes we need to implement.

1. kubechecks to have a watcher on the multiple argo-cd
2. how to tell which MR is for which argo-cd server (implement a config file like .kubechecks.yaml on the argo-cd-configs repo so kubechecks can tell which app/appsets to compare to?)
3. multiple argo-cd api keys

@djeebus can you think of anything else?