Capability to enable custom plugins for Kustomize and helm plugins for kustomize

[dc588]

Proposed Feature

Can we add a feature to set kustomize build options to enable alpha-plugins and enable helm similar to argocd? Could this be added to an option to the kargo controller.

Motivation

We have custom transformers in kustomize to handle environment and cluster specific configuration. Having this feature will help us to transition to use kargo as our CD tool

Suggested Implementation

Can the kargo deployment be updated to enable custom kustomize plugins. Can we also incorporate with helm install as well?

[hiddeco]

We do at present no longer shell out to kustomize, but rather use the lower-level build API of it to ensure Project and Promotion boundaries are guarded, and it is safe to use for multi-tenant setups. The same applies to helm, where we use the Go equivalent of running helm template using the Helm SDK.

Furthermore, Kustomize plugins come in two (non-deprecated) flavors:

1. Containerized KRM Functions
2. Exec KRM Functions

Supporting the first option within Kubernetes itself is difficult because it needs to spawn a container to be able to work. The second option has a better chance of being supported (although I potentially see dependency issues if someone were to attempt to use a Ruby script as shown in the example), but requires discussion and exploration to see if and/or how we can safely enable this.