pkg/k8sclient: expose the kubernetes client

[awprice]

Exposing the underlying kubernetes client will provide the flexibility of
allowing the user to perform more advanced actions that the SDK does not
provide out of the box. Often, more advanced actions are located in
subresources of the resource, like Pods().Evict and Pods().GetLogs. The SDK
does not provide access to these, and restricts the user to create, get,
update, delete and list.

Some examples:

kubeClient := k8sclient.GetKubeClient()

// Evict pod
kubeClient.CoreV1().Pods("default").Evict(&v1beta1.Eviction{})

// Get pod logs
kubeClient.CoreV1().Pods("default").GetLogs("example", &v1.PodLogOptions{})

Resolves #190

[andersjanmyr]

👍 I have done this in my fork of the project too. This is definitely something that is needed while the project is maturing.

[hasbro17]

@awprice LGTM. Can you please update the CHANGELOG as well. Just add The SDK exposes the Kubernetes clientset via k8sclient.GetKubeClient() #295.

[awprice]

@hasbro17 Awesome. I've just updated the changelog to include that line.
@andersjanmyr Yep, definitely agree that it's needed whilst the project is maturing.

[hasbro17]

@awprice Were you able to manually test this out, i.e successfully use the client returned by k8sclient.GetKubeClient() to create/update resources.
We're still working on adding e2e tests so we'll need to test this manually for now.

[awprice]

@hasbro17 Apologies, I've updated the commit to fix an issue where the kubeClient is nil.

I've tested the change with the following actions:

• Creating pods
• Updating pods
• Deleting pods

More advanced actions:

• Using the Discovery API to determine if eviction is supported on the API server
• Evicting pods