Create an 'apis' golang module to minimize dependencies for clients

[dprince]

- What I did

Create new apis module so that external projects can leveral the MCO API structs without importing the larger set of dependencies at the projects top level go.mod file.

- How to verify it

Once landed projects can import github.com/openshift/machine-config-operator/pkg/apis instead of github.com/openshift/machine-config-operator (~90% reduction in go.sum file contents...)

- Description for the changelog

This patch creates a new './pkg/apis' go module with
the existing MCO API which makes it possible for
external projects to import the API structs for
MCO without the larger set of dependencies in the projects
top level go.mod

See notes on multiple go.mod files in the same repository here:
https://github.com/golang/go/wiki/Modules#should-i-have-multiple-modules-in-a-single-repository
(See the "Two example scenarios where it can make sense to have more than one go.mod in a repository" section).

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[sinnykumari]

Many thanks for the PR!

I am not sure if we want to go in this direction. Ideally MCO APIs and CRDs has to be moved to https://github.com/openshift/api repo where majority of OpenShift related apis lives. There has been multiple attempts from MCO team to perform this move, most recent one was in openshift/api#1060 . This is still in our radar and we would like to make switch once we are able to prioritize the work.
Can you help us understand if it will still make sense or we should close this in favor of moving MCO APIs to centralized openshift/api location?

[dprince]

Can you help us understand if it will still make sense or we should close this in favor of moving MCO APIs to centralized openshift/api location?

I think either pattern is valid. This was quite easy to implement. It solves the problem albeit leaving them in this repo instead of moving to openshift/api. It also seems to adhere to exceptions for when you might want multiple modules in a repo:

https://github.com/golang/go/wiki/Modules#should-i-have-multiple-modules-in-a-single-repository

That said if the decision above is to use openshift/api that works too. Would be nice to have it sooner rather than later though as the security patches due to some of the MCO dependencies are becoming noticable. Is someone actively working on the effort still? If not perhaps I can help.

[sinnykumari]

Is someone actively working on the effort still? If not perhaps I can help.

Not at the moment. If you can help, that will be great. Let us know if you would like to work on it :)