[chore] move controllers under internal

[atoulme]

Description:
Move controllers under internal so their API is not exported.

[swiatekm]

This placement of controllers is a kubebuilder standard. I'm not sure how much that matters to us at this point, but it would certainly make the migration to kubebuilder v4 more difficult. WDYT @open-telemetry/operator-approvers ?

[jaronoff97]

Yes, i think we should do the kubebuilder v4 migration first as that unblocks a few other issues IIRC.

[atoulme]

I don't see an issue for moving to kubebuilder 4, is it ok to open one? Is anyone working on it?

[frzifus]

I dont see a huge downside of exposing it or benefit of moving it into internal here. Thats why I would prefer to just follow whatever kubebuilder standard is.

[atoulme]

The problem is that you're currently exposing incomplete APIs. It is possible other downstream projects may start to depend on it and bind you to a specific go API, which doesn't seem to be the intent of this project. See
https://pkg.go.dev/github.com/open-telemetry/opentelemetry-operator@v0.116.0/controllers

[atoulme]

I am reading through kubebuilder resources; I see a reference to controllers in the kubebuilder book, but it's placed under internal:
https://book.kubebuilder.io/cronjob-tutorial/controller-implementation

https://github.com/kubernetes-sigs/kubebuilder/blob/master/docs/book/src/cronjob-tutorial/testdata/project/internal/controller/cronjob_controller.go

Is there a reference elsewhere to placing controllers under top level folder?

[swiatekm]

It used to be at top level in v2: https://book-v2.book.kubebuilder.io/cronjob-tutorial/controller-implementation.

I guess if it's under internal in subsequent versions, then moving it right now won't really make the migration any more difficult.