WIP: Supersedes #3
I don't know a better way to expect these command line options, I've just replaced them with optional defaults here that worked for my example use case. Supersedes PR #3 which fixed an earlier issue I had with this plugin.
This probably isn't getting merged anywhere as-is, but maybe having this PR open will help other people that find this issue against kubectl v1.13 and newer API clients that have breaking plugin API changes. This trick still works great against my reasonably current AKS cluster version!
The plugin also can't be named exec-user anymore according to kubectl plugin list which emits a warning expecting the plugin name with dashes in it to avoid shadowing built-ins.
https://kubernetes.io/docs/tasks/extend-kubectl/kubectl-plugins/#name-conflicts-and-overshadowing