[feature] allow more helm value sources

[simonostendorf]

I would like to get helm values from other sources than ConfigMap or Secrets.

I think it would be really useful to allow every kind of kubernetes resource and specify a path where the value should be read from.

Example:

I have a CRD called MyProviderNetwork. The controller for this crd creates a new cloud provider network in the background and writes the id to .status.networkId. It would be really cool to read this value as a flux value.

Example Configuration for Flux:

apiVersion: helm.toolkit.fluxcd.io/v2
kind: HelmRelease
...
spec:
  valuesFrom:
    - kind: MyProviderNetwork
      name: resource-name
      valuesKey: helmValueWhereNetworkIdShouldBeWritten
      path: .status.networkId
      optional: false