wip: packagevariant controller: support namespacing target packages

[natasha41575]

Not yet ready for review.

Related issue: #3488

Adds the set-namespace function to target downstream packages using the package-context pattern. This should result in the target packages' resources ending up with the specified namespace set on them.

[johnbelamaric]

Thanks Natasha. I don't necessarily want to tie this directly to the package context pattern. In fact, I think that pattern is already supported without this change. If the user sets the package name as different from the upstream, and adds set-namespace in the package Kptfile, I think the existing code should already handle this.

The package context pattern for set-namespace is really around packages whose purpose is to provision namespaces - that is, the package name matches the namespace name. The idea of putting namespace in here is for packages that need to be installed in a namespace, we are making namespace and explicit input to the package variant. It's really a special case of general "mutation" that we are building in directly since it is so common.

Along those lines, I have been talking pretty extensively with the Nephio team on what we need from PackageVariant and would like to evolve the API a bit. I will put in a PR for a design proposal that evolves this to the next step, and then once we all agree I'll work on implementation along with whoever is able to contribute.

[natasha41575]

Thanks for your feedback @johnbelamaric! If I am interpreting your comment correctly, this PR is not needed and you are planning to submit a design proposal for api changes that you/Nephio need.

In that case, I'll close this PR, focus on getting #3764 merged, and await your proposal.

[johnbelamaric]

Oh, I didn't actually mean that, but I think it's OK to pause on this PR until the proposal is ready and we can debate it.