Docker Support

Some layers might have "mediaType": "application/vnd.docker.image.rootfs.foreign.diff.tar.gzip" which are not present on the registry.

In this case client will not go to the registry to fetch the layer( because it is not there) but will follow the url which is specified among other details of layer.

Pulp should not try to fetch it from registry during sync , but simply skip, it also does not want to follow the url and download the layer because it might violate the license.
Pulp would also not create any record in DB for that layer.

$ ./docker-token portainer/portainer@windows-amd64-1.13.0
{
  "schemaVersion": 2,
  "mediaType": "application/vnd.docker.distribution.manifest.v2+json",
  "layers": [
    {
      "mediaType": "application/vnd.docker.image.rootfs.foreign.diff.tar.gzip",
      "digest": "sha256:bce2fbc256ea437a87dadac2f69aabd25bed4f56255549090056c1131fad0277",
      "size": 252691002,
      "urls": [
        "https://go.microsoft.com/fwlink/?linkid=837858"
      ]
    },
    {
      "mediaType": "application/vnd.docker.image.rootfs.foreign.diff.tar.gzip",
      "digest": "sha256:4a8c367fd46d2e2da2a8b0fa02158540e13b3a9015daf9f17d1af354a591492f",
      "size": 121971948,
      "urls": [
        "https://go.microsoft.com/fwlink/?linkid=848906"
      ]
    },
    {
      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
      "digest": "sha256:feedefe2c110863b761bb71ba7199fefe1058afecbe68752d051c2ca0899e266",
      "size": 3684048
    },
    {
      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
      "digest": "sha256:bb652e12abcfb1b0681c29dcff44a842f54869d6a5d6c57de1523b275af77c17",
      "size": 952
    },
    {
      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
      "digest": "sha256:4addfdf3b551b41da10b28fb9e0e0702d568e68ce2330183220384358f0f7d9c",
      "size": 947
    },
    {
      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
      "digest": "sha256:ad5cdcb7aa1e047a4ac348b74b5652c8a16fcb3dd013c288f8e65a095995c1d4",
      "size": 948
    },
    {
      "mediaType": "application/vnd.docker.image.rootfs.diff.tar.gzip",
      "digest": "sha256:6bd5a5818cacdc9744192da603a8765e793ac1b5dcb1bf1efacbe81df875ea06",
      "size": 943
    }
  ],
  "config": {
    "mediaType": "application/vnd.docker.container.image.v1+json",
    "digest": "sha256:7cc9ff24526dfffdb8c188e6bae7e11d75d1ac5731d85e6fdccd5c7382d84207",
    "size": 2369
  }
}