Add support for OCI Image Index

OCI Image Index (https://github.com/opencontainers/image-spec/blob/v1.0.1/image-index.md)
is similar to vnd.docker.distribution.manifest.list.v2

This revives #244 originally created by @luizribeiro

A testing client could pull koenkk/zigbee2mqtt:latest with this change.

Fixes #243

Author: chantra

src/mediatypes.rs

@@ -36,6 +36,10 @@ pub enum MediaTypes {
     #[strum(serialize = "application/vnd.oci.image.manifest.v1+json")]
     #[strum(props(Sub = "vnd.oci.image.manifest.v1+json"))]
     OciImageManifest,
+    // OCI Image index
+    #[strum(serialize = "application/vnd.oci.image.index.v1+json")]
+    #[strum(props(Sub = "vnd.oci.image.index.v1+json"))]
+    OciImageIndexV1,
     /// Generic JSON
     #[strum(serialize = "application/json")]
     #[strum(props(Sub = "json"))]
@@ -60,6 +64,7 @@ impl MediaTypes {
                     ("vnd.docker.image.rootfs.diff.tar.gzip", _) => Ok(MediaTypes::ImageLayerTgz),
                     ("vnd.docker.container.image.v1", "json") => Ok(MediaTypes::ContainerConfigV1),
                     ("vnd.oci.image.manifest.v1", "json") => Ok(MediaTypes::OciImageManifest),
+                    ("vnd.oci.image.index.v1", "json") => Ok(MediaTypes::OciImageIndexV1),
                     _ => Err(crate::Error::UnknownMimeType(mtype.clone())),
                 }
             }

src/v2/config.rs

@@ -115,6 +115,7 @@ impl Config {
                     (MediaTypes::ManifestV2S1Signed, Some(0.4)),
                     (MediaTypes::ManifestList, Some(0.5)),
                     (MediaTypes::OciImageManifest, Some(0.5)),
+                    (MediaTypes::OciImageIndexV1, Some(0.5)),
                 ],
                 // GCR incorrectly parses `q` parameters, so we use special Accept for it.
                 // Bug: https://issuetracker.google.com/issues/159827510.
@@ -124,6 +125,7 @@ impl Config {
                     (MediaTypes::ManifestV2S1Signed, None),
                     (MediaTypes::ManifestList, None),
                     (MediaTypes::OciImageManifest, None),
+                    (MediaTypes::OciImageIndexV1, None),
                 ],
             },
         };

src/v2/manifest/mod.rs

@@ -87,7 +87,7 @@ impl Client {
                     content_digest,
                 ))
             }
-            mediatypes::MediaTypes::ManifestList => Ok((
+            mediatypes::MediaTypes::ManifestList | mediatypes::MediaTypes::OciImageIndexV1 => Ok((
                 res.json::<ManifestList>().await.map(Manifest::ML)?,
                 content_digest,
             )),