Support for NewRelic - Deployment Marker API

[saviogl]

Support for adding New Relic as a notification service for ArgoCD notifications. New Relic has the concept of Deployment Markers that allows us to register a custom event as a deployment to be correlated with other observability metrics.

By adding this integration anyone using New Relic can easily rely on it to automatically create deployment markers upon application deployments. Within the GitOps model this will also yield markers for configuration changes beyond regular application code change which makes for a pretty holistically approach for production management and observability.

It can look something like this

apiVersion: v1
kind: ConfigMap
metadata:
  name: <config-map-name>
data:
  service.mattermost: |
    apiURL: <api-url>
    apiKey: $newrelic-apiKey

apiVersion: v1
kind: Secret
metadata:
  name: <secret-name>
stringData:
  newrelic-apiKey: apiKey

apiVersion: argoproj.io/v1alpha1
kind: Application
metadata:
  annotations:
    notifications.argoproj.io/subscribe.<trigger-name>.newrelic: <app-id>