#86 Build plugin and images for multiple architectures

[larhauga]

This adds support for building and publishing linux-amd64 and linux-arm64 versions of the plugin.

This fixes #86

See https://github.com/larhauga/opa-docker-authz/actions for example run and https://github.com/larhauga/opa-docker-authz/pkgs/container/opa-docker-authz for published package

I have only gotten this to work by explicitly pinning to the tag edge-linux-arm64/edge-linux-amd64 and I think we can live with this solution in the interim.

---

Details regarding multi-arch manifest list

When trying to build a manifest list for a multi-arch tag, it does not work, and we get the following error that seems to be coming from here: https://github.com/moby/moby/blob/master/plugin/backend_linux.go#L203

msg="Handler for GET /v1.44/plugins/privileges returned error: did not find plugin config for specified reference ghcr.io/larhauga/opa-docker-authz:edge"
Error response from daemon: did not find plugin config for specified reference ghcr.io/larhauga/opa-docker-authz:edge

I have created a Q&A at the moby repo to get some input on this: moby/moby#47369

The manifests created with docker manifest does not create a manifest usable by the docker plugin system. For future references a custom manifest can be created in the following way:

curl -X PUT -H "Authorization: Bearer $(echo $GITHUB_TOKEN|base64)" -H "Content-Type: application/vnd.docker.distribution.manifest.v2+json" --data @manifest.json https://ghcr.io/v2/${{ github.repository }}/manifests/edge

This is the edge-linux-amd64 manifest.

{
        "schemaVersion": 2,
        "config": {
                "mediaType": "application/vnd.docker.plugin.v1+json",
                "digest": "sha256:f588fb1f8e38f38b53d49c1b79281b36c2ca64b2b16119c1c8c5b6019af7d6c6",
                "size": 836
        },
        "layers": [
                {
                        "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
                        "digest": "sha256:18eeb142bdc5e4d0b518e1b1321fa0a4863b21248ba614e07d4dcd87966e3d31",
                        "size": 13257330
                }
        ],
        "mediaType": "application/vnd.docker.distribution.manifest.v2+json"
}

The :edge manifest:

{
   "schemaVersion": 2,
   "mediaType": "application/vnd.docker.distribution.manifest.list.v2+json",
   "manifests": [
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 419,
         "digest": "sha256:9b40bdeec15886807829ef61be7483bbc556758176944426965220cc2afe0f52",
         "platform": {
            "architecture": "amd64",
            "os": "linux"
         }
      },
      {
         "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
         "size": 419,
         "digest": "sha256:aac32815a31f558589e17ed28deeb500c482d557d9038710f4e84177941d10a1",
         "platform": {
            "architecture": "arm64",
            "os": "linux"
         }
      }
   ]
}

[anderseknert]

Thanks! Just a few nits, but looks good 👍

[anderseknert]

Thanks! Let's give it a try :)