Infer predefined annotations when pushing to registry

[itowlson]

Fixes #2612 (or at least part of it).

I'm not sure the best way to test this in CI, but trying it locally it seems promising:

# Manifest for testing
ivan@hestia:~/testing$ cat v2vanillareallyv2/spin.toml
spin_manifest_version = 2

[application]
name = "v2vanillareallyv2"
version = "0.1.0"
authors = ["itowlson <ivan.towlson@fermyon.com>"]
description = ""
# moar TOML

# If the user doesn't set any of the predefined annotations
ivan@hestia:~/testing$ spin registry push localhost:5000/vanilla:v0.1 -f v2vanillareallyv2/ --insecure
Pushing app to the Registry..
Pushed with digest sha256:9110a84446a12c3479978316e2343e60bda6d5375ff39fb0ef0f77759d7d1011

# ...then they are inferred (formatting added for legibility)
ivan@hestia:~/testing$ docker buildx imagetools inspect localhost:5000/vanilla:v0.1 --raw
{"annotations":{
  "org.opencontainers.image.authors":"itowlson <ivan.towlson@fermyon.com>",
  "org.opencontainers.image.created":"2024-07-09T01:33:37.290049791+00:00",
  "org.opencontainers.image.title":"v2vanillareallyv2",
  "org.opencontainers.image.version":"0.1.0"
},
# moar JSON
}

# But if the user specifies, say, the `authors` annotation...
ivan@hestia:~/testing$ spin registry push localhost:5000/vanilla:v0.2 -f v2vanillareallyv2/ --insecure --annotation org.opencontainers.image.authors="THE GREAT OZ"
Pushing app to the Registry..
Pushed with digest sha256:63420c721dbb51261c0c3af18cded3b6ef81d8fc65c820be535500f27cb4285e

# ...then we do not infer it but respect the one we are given (formatting added for legibility)
ivan@hestia:~/testing$ docker buildx imagetools inspect localhost:5000/vanilla:v0.2 --raw
{"annotations":{
  "org.opencontainers.image.authors":"THE GREAT OZ",
  "org.opencontainers.image.created":"2024-07-09T01:36:01.402920121+00:00",
  "org.opencontainers.image.title":"v2vanillareallyv2",
  "org.opencontainers.image.version":"0.1.0"
},
# moar JSON
}

The OCI authors annotation is a string, whereas Spin allows an array: the PR comma-space-concatenates them, e.g. "The Great Oz, Dorothy Gale". OCI describes the field as a freeform string but if there's a common community convention then I can adopt that.

This PR does not provide a way for a user to suppress inference but the infrastructure is there in case we want to add an option, or for programmatic use (e.g. reproducibility).

[itowlson]

Also linked #2259

[radu-matei]

The fact that annotations is an option of a map and predefined_annotations is an enum is somewhat confusing here; how much of this behavior is an external consumer of this API supposed to understand?

[itowlson]

@radu-matei I am gazing at this and struggling to think of a better design. I don't want to put it on consumers to construct the predefined annotations, so it shouldn't be a map. So I am having difficulty getting away from the "I want the predefined annotations or I don't" flag. I would value suggestions. Or is it as simple as "we should rename the flag to infer_predefined_annotations or something, so it sounds like an action instead of a set" perhaps?

[itowlson]

@radu-matei I tried some renaming - if that doesn't improve matters then I'd value suggestions - thanks!

[radu-matei]

So the behavior here is: always infer, and if the user provided any annotation explicitly, it takes priority over the inferred value??

[itowlson]

If the user provides one of the annotations that would be inferred explicitly, then the explicit value takes precedence - see the comment on the enum.

[vdice]

Nice, thanks Ivan!

[vdice]

OCI describes the field as a freeform string but if there's a common community convention then I can adopt that.

Not able to find a convention after a brief search. I think the comma-separated string as you've initially added seems a sane way to go for now.

[vdice]

🎸👨‍🎤 🔈 LGTM+11!