Allow to provide custom OCI annotations

[hpedrorodrigues]

Hey 👋🏻

Description

This pull request basically allows to provide custom OCI annotations to be added to the final artifacts (using either apko-publish or apko-snapshot actions).

If we want to add annotations without these changes, we likely need to use a separate action to update the config file before calling apko-publish (or apko-snapshot) (see example) or implement some other workaround. The main idea here is to make this process easier.

Basic Testing

• apko-publish: this version worked well here (see job, for instance).

example manifest

revision, created, and version are the annotations we are interested in.

♪ crane manifest ghcr.io/hpedrorodrigues/envsubst:1.30.1 | jq
{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.index.v1+json",
  "manifests": [
    {
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "size": 916,
      "digest": "sha256:661b18f68e995e9171e1a60e0836a9ebbcc0344f299057e80c29b8efc7520df3",
      "platform": {
        "architecture": "amd64",
        "os": "linux"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "size": 916,
      "digest": "sha256:55deeb9f2a1193a5caa3c3d254f13e93e535974a50af5bc1e04f66fb1ace4a1b",
      "platform": {
        "architecture": "arm64",
        "os": "linux"
      }
    }
  ],
  "annotations": {
    "org.opencontainers.image.authors": "Pedro Rodrigues <github.com/hpedrorodrigues>",
    "org.opencontainers.image.created": "2024-03-16T04:14:31",
    "org.opencontainers.image.description": "Simple image wrapping envsubst (gettext)",
    "org.opencontainers.image.revision": "06e805cea68b238bde5c297ecaf4436219b80d2c",
    "org.opencontainers.image.source": "https://github.com/hpedrorodrigues/images/tree/main/envsubst",
    "org.opencontainers.image.title": "envsubst",
    "org.opencontainers.image.version": "1.30.1"
  }
}

• apko-snapshot: this version is working well here (see job, for instance).

example manifest

revision, created, and version are the annotations we are interested in.

♪ crane manifest ghcr.io/hpedrorodrigues/envsubst:1.47.1 | jq
{
  "schemaVersion": 2,
  "mediaType": "application/vnd.oci.image.index.v1+json",
  "manifests": [
    {
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "size": 916,
      "digest": "sha256:204151eafbcf0ef6ed1b9b06638f58c82d6567b65f04f947f6eb7f4d3e1f074e",
      "platform": {
        "architecture": "amd64",
        "os": "linux"
      }
    },
    {
      "mediaType": "application/vnd.oci.image.manifest.v1+json",
      "size": 916,
      "digest": "sha256:7346a405e766c3ba82cbf53e4635b4696c5643da3bc2c4529a1fda33e2f8e61a",
      "platform": {
        "architecture": "arm64",
        "os": "linux"
      }
    }
  ],
  "annotations": {
    "org.opencontainers.image.authors": "Pedro Rodrigues <github.com/hpedrorodrigues>",
    "org.opencontainers.image.created": "2024-03-17T19:44:53",
    "org.opencontainers.image.description": "Simple image wrapping envsubst (gettext)",
    "org.opencontainers.image.revision": "d9d40e00117119c1990afdadfe47fa2dd88f1756",
    "org.opencontainers.image.source": "https://github.com/hpedrorodrigues/images/tree/main/envsubst",
    "org.opencontainers.image.title": "envsubst",
    "org.opencontainers.image.version": "1.47.1"
  }
}

---

Let me know if these changes make sense for this project or if you have any concerns.

[hpedrorodrigues]

We allow providing this input to apko-build and apko-publish.
Since I'm also interested in it, I'm taking the opportunity to add it to this action.
Let me know if it makes sense to keep it here.