fix(kuma-cp) create new object from resource descriptor

[jakubdyszkiewicz]

Summary

It is not an issue with the current code but it's a trap that we can easily fall into.

ResourceDescriptor has a method NewObject(), but in order to call it, it needs to set internal objectType and listType fields. Those fields are set by InitDescriptor() method which is only called when the descriptor is put into ResourceRegistry.

The problem is that the ResourceDescriptor can also be retrieved from .Descriptor() method of the object and this copy of an object does not contain initiated objectType and listType which results in panic.

I moved the retrieving resource type to NewObject itself, I don't think we should be able to create an object which requires extra initialization, especially if the object is copied around instead of passing a pointer.

The alternative would be to template resource-gen with model.InitDescriptor when the descriptor is generated in the code, but I don't like the fact we can create a struct that is not functional.

Issues resolved

No issues.

Documentation

• No docs, internal changes.

Testing

• Unit tests
• E2E tests
• Manual testing on Universal
• Manual testing on Kubernetes

Backwards compatibility

• No backporting

[lahabana]

Sounds like a sensible change!

[jpeach]

Good find!