fix(KustomizeUpdater): non docker.io image registries were ignored for image updates

[oleksandr-codefresh]

Fix for issue:
Update Argo CD Application Image Tags for kustomize apps does commit any changes during deployment if image pushed to non-default registry ( docker.io )

images:
  - name: vplakydatestregistry.azurecr.io/xeonalex/guesbook-unprivileged
    newTag: "latest"

⚠️ Does this change require a corresponding Server Change?
⚠️ If so - please add a "Requires Server Change" label to this PR!

[rain-on]

That test is great, exposes the problem nicely 🙏

Having looked at the code, I'm actually wondering if the real problem is ImageReplacementResult.updatedImageReferences.

Originally this field was just used for sticking into the Git commit message, and so a string was appropriate.
However, its not a FULL representation of what was changed in the file-update, as it strips out the registry data - i.e. the problem we're seeing is due to this loss of information.

I THINK I'd recommend we update the KustomizeImageReplacer to appear:

This would ensure we don't strip the registry data - this would also solve this problem, and probably in a nicer way ... I think.

If we went down this road, we'd probably need to apply this to all ImageReplacers, not just Kustomize.

If you wanted to go to an ever better solution - I'd change the updatedImageReferences and alreadyUpToDateImages from strings to ContainerImageReference - then we're passing back TYPED data, which makes it much safer to use in "business logic" (Rather than plain strings).

eg:
public class ImageReplacementResult(string updatedContents, HashSet<ContainerImageReference> updatedImageReferences, HashSet<ContainerImageReference> alreadyUpToDateImages, HashSet<string>? unrecognisedKinds = null)

Final thought - we probably want to apply this to 2026.2 release branch, then let TeamCity merge it forward onto main.

[oleksandr-codefresh]

reopened under https://github.com/OctopusDeploy/Calamari/pull/2011/changes