Provid Support for Alterative SourceRef's

[rawkode]

I have a controller running that can monitor the source-controller types (Git, OCI, Bucket) for revisions and allowed for third-party transformations (cdk8s, CUE, Dhall, jsonnet).

My plan was to feed this back to FluxCD and allow the kustomize-controller to apply, but unfortunately that isn't possible because of the Kind checks.

I'd like to propose that FluxCD supports external / alternative sources provided they have .status.Artifact that can be deserialised.

[aryan9600]

There are several ideas around how to support source files other than Kubernetes yaml. We have been internally discussing different avenues on how to enable this, such as introducing a new Artifact API or simply using duck typing to fetch an arbitrary resource that promises to have a .status.artifact. We want to publish an RFC soon, so that we can start work on this.

[stefanprodan]

This is covered by: https://github.com/fluxcd/flux2/pull/5292