K8S user impersonation

[Dimpison]

Describe the bug
This k8s client doesn't allow impersonating another user/SA in a cluster. kubectl binary allows doing this via --as flag or adding the following entity to kubeconfig: users.user.as. Even adding the entity to kubeconfig,

Client Version
1.1.0

Server Version
1.30.10

To Reproduce
Steps to reproduce the behavior:
Run the following code.

import * as k8s from "@kubernetes/client-node";
const kubeconfigPath = "/path/to/kube/config;
const kubeConfig = new k8s.KubeConfig();
kubeConfig.loadFromFile(kubeconfigPath);
console.log(kubeConfig.getCurrentUser());

The above code snippet doesn't show the users.user.as field even if it's added to the kubeconfig. As well as the client ignores the field when making a request to K8S API.

Kubeconfig snippet example:

- name: sudo user
  user:
    exec:
      apiVersion: client.authentication.k8s.io/v1beta1
      args:
      - eks
      - get-token
      - --cluster-name=cluste-name
      command: aws
    as: sudo-user

Expected behavior
It's expected that as field is available and can be used to impersonate user in k8s cluster.

Example Code

import * as k8s from "@kubernetes/client-node";
const kubeconfigPath = "/path/to/kube/config;
const kubeConfig = new k8s.KubeConfig();
kubeConfig.loadFromFile(kubeconfigPath);
console.log(kubeConfig.getCurrentUser());

Environment (please complete the following information):

• OS: [e.g. Windows, Linux]: MacOS
• Node.js version [eg. 20] - 20
• Cloud runtime [e.g. Azure Functions, Lambda] - local run

Additional context
Link to k8s doc https://kubernetes.io/docs/reference/access-authn-authz/authentication/#user-impersonation
Link to kubeconfig api reference https://kubernetes.io/docs/reference/config-api/kubeconfig.v1/#AuthInfo

[Soubi8]

This is really important and has to be addressed

[brendandburns]

Happy to review PRs if you want to add this.

[cjihrig]

@Dimpison can you give the changes in #2373 a try.

[Dimpison]

The issue and PR are being discussed in more detail in the PR (for visibility).

[cjihrig]

Closed by #2373