update: Package verification refactoring

go.mod

@@ -7,7 +7,6 @@ require (
 	github.com/notaryproject/notation-core-go v0.2.0-beta.1
 	github.com/opencontainers/go-digest v1.0.0
 	github.com/opencontainers/image-spec v1.1.0-rc2
-	github.com/oras-project/artifacts-spec v1.0.0-rc.2
 	github.com/veraison/go-cose v1.0.0-rc.1.0.20220824135457-9d2fab636b83
 	oras.land/oras-go/v2 v2.0.0-rc.4
 )

go.sum

@@ -16,8 +16,6 @@ github.com/opencontainers/go-digest v1.0.0 h1:apOUWs51W5PlhuyGyz9FCeeBIOUDA/6nW8
 github.com/opencontainers/go-digest v1.0.0/go.mod h1:0JzlMkj0TRzQZfJkVvzbP0HBR3IKzErnv2BNG4W4MAM=
 github.com/opencontainers/image-spec v1.1.0-rc2 h1:2zx/Stx4Wc5pIPDvIxHXvXtQFW/7XWJGmnM7r3wg034=
 github.com/opencontainers/image-spec v1.1.0-rc2/go.mod h1:3OVijpioIKYWTqjiG0zfF6wvoJ4fAXGbjdZuI2NgsRQ=
-github.com/oras-project/artifacts-spec v1.0.0-rc.2 h1:9SMCNSxkJEHqWGDiMCuy6TXHgvjgwXGdXZZGXLKQvVE=
-github.com/oras-project/artifacts-spec v1.0.0-rc.2/go.mod h1:Xch2aLzSwtkhbFFN6LUzTfLtukYvMMdXJ4oZ8O7BOdc=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=

internal/envelope/envelope.go

@@ -0,0 +1,10 @@
+package envelope
+
+import (
+	ocispec "github.com/opencontainers/image-spec/specs-go/v1"
+)
+
+// Payload describes the content that gets signed.
+type Payload struct {
+	TargetArtifact ocispec.Descriptor `json:"targetArtifact"`
+}