Design K8sClient abstract interface that will abstract underlying calls

[hattan]

The goal of this design is to create a proposal for a high level abstraction for use in writing tests against Kubernetes in Benchpress.

Parent: #353

Initial spike:

BeforeAll {
  Import-Module BenchPress.Kubernetes

}

Describe 'Verify Pods' {
  It "Should contain 5 pods, when a kubeconfig is explicitly provided" {
    # arrange
    $params = @{
      KubeConfigFile     = "<path>"
    }

    $pods = Get-Pods $params

    # act and assert
    $pods.length | Should -Be 5
  }

  It "Should contain 5 pods, when the environment variable KUBECONFIG is set" {
    # arrange
    $Env:KUBECONFIG = "<path to kubeconfig file"

    $pods = Get-Pods 

    # act and assert
    $pods.length | Should -Be 5
  }  

  It "Should contain 5 pods and use the default kubeconfig when no file or environment variable is set" {
    # arrange

    # should use the default kubeconfig
    $pods = Get-Pods 

    # act and assert
    $pods.length | Should -Be 5
  }    
}

AfterAll {
  Get-Module BenchPress.Kubernetes | Remove-Module
}

[hattan]

Implementation should create a KubernetesClient object under the hood and have different implementations for either a kubectl implementation or one using the dotnet sdk.

To level functions shouldn't call the KubernetesClient directly as it will be a private implementation method (Similar to BenchPress's Account module)