Setup ArgoCD webhook

Overview

Argo CD polls Git repositories every three minutes to detect changes to the manifests. To eliminate this delay from polling, it can be configured receive webhook events when MRs are merged so that it can sync immediately.

Documentation: https://argo-cd.readthedocs.io/en/latest/operator-manual/webhook/

Exit criteria

• A webhook to ArgoCD is configured in https://gitlab.com/gitlab-com/gl-infra/argocd/apps