Allow the Applicationset policy to be set on ApplicationSet object instead of global flag

[jdomag]

Summary

The policy is set per whole controller, while it should be set per ApplicationSet object.

Motivation

We use staging and dev environments on the same k8s cluster separated by namespace. For staging it's not allowed to override Application parameters and applicationset policy=create-update should be applied. For dev namespaces it's totally fine to edit application parameters from cli or gui - for example to switch target branch to simplify testing of changes in helm charts. In that case we need policy=create-only to be set.

Proposal

default policy field can be overridden by spec of ApplicationSet object.

[nhuray]

It's definitely a feature all ArgoCD users would benefit. At the moment the workaround is to deploy 2 ArgoCD instances.