Before this change, we simply did a search/replace on the
stringified kubeconfig blob.
Now we're parsing it into a kubeconfig struct and modify the fields
directly in a more controlled manner.
Here's what we change:
- server URL: based on the chosen APIHost and APIPort
- cluster name: default -> k3d-CLUSTERNAME
- user name: default -> admin@k3d-CLUSTERNAME
- context name: default -> admin@k3d-CLUSTERNAME
