Introduce the component system for managing pre-installed addons

[dghubble]

• Previously: Typhoon provisions clusters with kube-system components like CoreDNS, kube-proxy, and a chosen CNI provider (among flannel, Calico, or Cilium) pre-installed. This is convenient since clusters come with "batteries included". But it also means upgrading these components is generally done in lock-step, by upgrading to a new Typhoon / Kubernetes release
• It can be valuable to manage these components with a separate plan/apply process or through automations and deploy systems. For example, this allows managing CoreDNS separately from the cluster's lifecycle.
• These "components" will continue to be pre-installed by default, but a new components variable allows them to be disabled and managed as "addons", components you apply after cluster creation and manage on a rolling basis. For some of these, we may provide Terraform modules to aide in managing these components.

module "cluster" {
  ...

  # defaults shown
  components = {
    enable = true
    coredns = {
      enable = true
    }
    kube_proxy = {
      enable = true
    }
    # Only the CNI set in var.networking will be installed
    flannel = {
      enable = true
    }
    calico = {
      enable = true
    }
    cilium = {
      enable = true
    }
  }
}

An earlier variable install_container_networking = true/false has been removed, since it can now be achieved with this more extensible and general components mechanism by setting the chosen networking provider enable field to false.

[kalmufti]

So with this new system, would this be the proper way to skip cilium and manage it on my own?

module "cluster" {
  ...
  networking  = "cilium"

  components = {
    cilium = {
      enable = false
    }
  }

or just set networking = "none"

[dghubble]

Yes, that example looks right. Typhoon does still need to know which CNI provider you've chosen in order to allow the right firewall / security policies between nodes.

Setting networking to none should cause a validation error.