Switch to makefile modules

[inteon]

Start using the makefile-modules solution to test, build and release the sample-external-issuer.

[cert-manager-prow]

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[SgtCoDFish]

I haven't reviewed every line of this (obviously!) but it looks like what I'd expect.

That said, while makefile-modules makes sense here for ease of maintenance, this is quite a different repo to our others in that we expect others to copy+paste this repo, effectively.

If we do that, we're encouraging issuer maintainers to use makefile-modules. Today mm is basically an implementation detail of how we maintain the cert-manager projects, but this change would encourage others to use it.

Have we as a group discussed that or thought about the implications of that? I'm not saying we definitely shouldn't do that, but it does feel worth a thought

[SgtCoDFish]

comment: Honestly kind of a shame to remove this - it would be a great easy way for external issuer maintainers to package up their issuer, no?

[erikgb]

If we do that, we're encouraging issuer maintainers to use makefile-modules. Today mm is basically an implementation detail of how we maintain the cert-manager projects, but this change would encourage others to use it.

Encouraging our users to use makefile-modules will force us to think a lot more around breaking changes. Do we really want this? I would prefer to keep no guarantees on compatibility for makefile-modules and just use it for our the projects that are maintained by us (the cert-manager team).

I think this project should be built around kubebuilder (as it is, more or less) and kept up to date. I saw this PR when considering preparing a PR for migrating away from the use of the long-term deprecated kube-rbac-proxy. Kubebuilder has already documented this migration, and I was planning to upgrade kubebuilder to fix this now urgent issue. See also https://kubernetes.slack.com/archives/CDEQJ0Q8M/p1734534667142689. But I don't want to do this with this PR undecided.

[wallrj]

I agree with @SgtCoDFish and @erikgb .
I want freedom to update and refactor makefile-modules without having to worry about breaking external issuers that have bootstrapped from this repo.
So I vote to close this PR.