Webhooks should have better names

[erikgb]

What

When attempting to delete a namespace with subnamespaces, this is rejected by the webhook - which is good. But I think webhooks should be named properly - so a user can understand better what's going on.

$ k delete namespaces erikbo
Error from server (Forbidden): admission webhook "vnamespace.kb.io" denied the request: child namespaces exist

How

Describe how to address the issue.

Checklist

• [ ] Finish implementation of the issue
• [ ] Test all functions
• [ ] Have enough logs to trace activities
• [ ] Notify developers of necessary actions

[zeroalphat]

@erikgb As your feedback, it looks like it should be fixed. We will fix it.