[FEATURE] Node Agents vs. Direct Cluster Interaction

[iwilltry42]

k3d has some features that interact with K3s functionality directly in one way or another:

• custom entrypoint scripts
• updating /etc/hosts
• updating CoreDNS (either directly in the live ConfigMap or on disk in auto-deploy manifest)
• ...

Some of those can only run at specific stages of the cluster lifecycle and can not be run after the cluster was created (due to the way they're implemented). For tasks that can be executed during the cluster runtime, we can choose one of the following ways:

1. Interact directly with the cluster, e.g. via kubectl or the Kubernetes-Client SDK
2. Have NodeAgents running inside the cluster (e.g. as a DaemonSet) and just passing in a Configfile (ConfigMap), e.g. via the auto-deploy manifests, to configure them