feat(artifact): add OCI references support (#936)

Thanks @jdolitsky et al for kicking off these changes at:
https://github.com/oci-playground/zot/commits/main

Thanks @sudo-bmitch for reviewing the patch

Signed-off-by: Ramkumar Chinchani <rchincha@cisco.com>

pkg/storage/s3/s3.go

@@ -1224,7 +1224,12 @@ func (is *ObjectStorage) GetBlobContent(repo string, digest godigest.Digest) ([]
 	return buf.Bytes(), nil
 }
 
-func (is *ObjectStorage) GetReferrers(repo string, digest godigest.Digest, mediaType string,
+func (is *ObjectStorage) GetReferrers(repo string, digest godigest.Digest, artifactType string,
+) (ispec.Index, error) {
+	return ispec.Index{}, zerr.ErrMethodNotSupported
+}
+
+func (is *ObjectStorage) GetOrasReferrers(repo string, digest godigest.Digest, artifactType string,
 ) ([]artifactspec.Descriptor, error) {
 	return nil, zerr.ErrMethodNotSupported
 }

pkg/storage/s3/s3_test.go

@@ -917,6 +917,18 @@ func TestNegativeCasesObjectsStorage(t *testing.T) {
 			So(err, ShouldNotBeNil)
 			So(err, ShouldEqual, zerr.ErrMethodNotSupported)
 		})
+
+		Convey("Test GetOrasReferrers", func(c C) {
+			imgStore = createMockStorage(testDir, tdir, false, &StorageDriverMock{
+				DeleteFn: func(ctx context.Context, path string) error {
+					return errS3
+				},
+			})
+			d := godigest.FromBytes([]byte(""))
+			_, err := imgStore.GetOrasReferrers(testImage, d, "application/image")
+			So(err, ShouldNotBeNil)
+			So(err, ShouldEqual, zerr.ErrMethodNotSupported)
+		})
 	})
 }