feat(kubelogin): add kubelogin azure ad auth

[haarchri]

Description of your changes

initial work done in crossplane-contrib/provider-helm#205 by @erhancagirici

Enables configuring Azure AD authentication via kubelogin integration. Introduces the type AzureServicePrincipalCredentials in ProviderConfig .spec.identity section.

The specified Azure Service Principal credentials provided via Secret, for authenticating to AKS cluster by obtaining a token through kubelogin

An example ProviderConfig using AzurePrincipalCredentials as identity for authenticating to AzureAD

apiVersion: kubernetes.crossplane.io/v1alpha1
kind: ProviderConfig
metadata:
  name: kubernetes-provider
spec:
  credentials:
    source: Secret
    secretRef:
      namespace: crossplane-system
      name: cluster-config
      key: kubeconfig
  identity:
    type: AzureServicePrincipalCredentials
    source: Secret
    secretRef:
      name: azure-credentials
      namespace: crossplane-system
      key: credentials.json

Fixes #105

I have:

• Read and followed Crossplane's contribution process.
• Run make reviewable test to ensure this PR is ready for review.

How has this code been tested

test image: index.docker.io/haarchri/provider-kubernetes:v0.0.0-130.g8467c56

 kubectl get objects
NAME                   KIND             PROVIDERCONFIG   SYNCED   READY   AGE
test-aks-5qft5         ApplicationSet   test-aks         True     True    16m
test-aks-f6mcm-gqthg   Secret           default          True     True    14m

- apiVersion: kubernetes.crossplane.io/v1alpha1
  kind: ProviderConfig
  metadata:
    name: test-aks
  spec:
    credentials:
      secretRef:
        key: kubeconfig
        name: 3a02bacd-0d8a-40b2-8922-560ba4acf7ed-akscluster
        namespace: upbound-system
      source: Secret
    identity:
      secretRef:
        key: credentials
        name: azure-creds
        namespace: upbound-system
      source: Secret
      type: AzureServicePrincipalCredentials

- apiVersion: kubernetes.crossplane.io/v1alpha1
  kind: ProviderConfig
  metadata:
    name: default
  spec:
    credentials:
      source: InjectedIdentity

[haarchri]

this error https://github.com/crossplane-contrib/provider-kubernetes/actions/runs/7267353656/job/19800977910?pr=170#step:11:1005 is related to: upbound/official-providers-ci#169

[erhancagirici]

Left one comment, otherwise LGTM

[turkenh]

Thanks @haarchri!