Implement wrappers in CLI module to allow working with older API versions

[xrstf]

Summary

This PR makes the kubectl kcp bind and kubectl kcp claims commands comatible with kcp 0.27+ at least, probably also older releases.

Currently our API does not have a shard, common type for APIBindings, and I did not want to embark in refactoring half the conversion logic just to fix this bug, plus it would have made backporting this into 0.28 impossible.

So instead I created a very lightweight wrapped in the CLI helpers. These turn the Kubernetes objects they wrap in kind of ActiveRecord-like objects that know how to refresh and update themselves, plus they know how to print or check their own status.

The goal was to try to keep the actual plugin logic as linear and typed as possible.

FAQ: Why are we not using the existing conversion funcs to handle permission claims? – because our conversion funcs do not do error handling, as they are meant to always succeed. More specifically, the conversion funcs for PermissionClaims assume that you have already pre-converted them in the APIBinding object to, if necessary, set annotations. This is simply not applicable here and so calling them would not help in detecting unsupported configurations.

What Type of PR Is This?

/kind regression

Related Issue(s)

Fixes #3529

Release Notes

The kcp kubectl plugin now supports kcp <0.28 again. In kcp 0.28+, `kubectl kcp claims get apibinding` now shows the permission claim verbs.

[embik]

/approve

[kcp-ci-bot]

LGTM label has been added.

Git tree hash: 9b1aa47ea323dd92b9310b7547ea8c5d56617ce9

[kcp-ci-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: embik

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[embik]

/cherry-pick release-0.28

[kcp-ci-bot]

@embik: once the present PR merges, I will cherry-pick it on top of release-0.28 in a new PR and assign it to you.

In response to this:

/cherry-pick release-0.28

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[xrstf]

/retest

[kcp-ci-bot]

@embik: new pull request created: #3541

In response to this:

/cherry-pick release-0.28

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.