Document upgrading an instance via the k8s API

[simonvane]

What would you like to be added:
Documentation of how to upgrade an instance via the k8s API.

Why is this needed:
We are using KUDO in a scenario where we need to automate our process. We cannot use kubectl in the process.

Further details:
Upgrading an instance is mentioned here using kubectl kudo upgrade <operatorname> --instance=<instanceName> [flags]. We would like to do the same using the k8s API.

It looks like the code that is run by the command above OperatorVerion which in turn calls UpdateInstance.

Would it be a safe approach to patch the instance with the following (as the UpdateInstance method does)?

{
  "spec": {
    "operatorVersion": {
      "name": "next-version-installed-in-the-cluster"
    }
  }
}