Notifications should be configurable via CR

Currently the Notifications feature in OpenShift GitOps when enabled requires editing existing secrets and configmaps to configure notification services, triggers, etc. This can be challenging to manage via a GitOps approach like ACM or a parent GitOps instance.

While it is possible to simply overwrite these instances, if users choose to do so they may miss out on improvements brought in by newer versions as they overwrite the configuration.

As a starting point, simply managing the services aspect including the secret (argocd-notifications-secret) and service definition in the configmap (argocd-notifications-cm) would be very helpful. Ideally the CR used for this should support referencing an external secret so that secret management tools (sealed-secrets, external-secrets, etc) can be used to manage this.

ACCEPTANCE CRITERIA

• Add fields to the Argo CD CRD to support reconciliation of notification resources through the Argo CD Operator.
     For example, users should not be modifying the notifications configmap directly, they should get this done through the Argo CD CRD. Operator should override the changes made to notification configmaps.