Define a formal manifest interface and implement in the schema1 and schema2 manifests

This will allow us to pass arbitrary manifests to the model

image/docker/schema1.py

@@ -18,9 +18,9 @@ from jwt.utils import base64url_encode, base64url_decode
 
 from digest import digest_tools
 from image.docker import ManifestException
+from image.docker.interfaces import ManifestInterface
 from image.docker.v1 import DockerV1Metadata
 
-
 logger = logging.getLogger(__name__)
 
 
@@ -85,7 +85,7 @@ class Schema1V1Metadata(namedtuple('Schema1V1Metadata', ['image_id', 'parent_ima
   """
 
 
-class DockerSchema1Manifest(object):
+class DockerSchema1Manifest(ManifestInterface):
   METASCHEMA = {
     'type': 'object',
     'properties': {
@@ -235,6 +235,10 @@ class DockerSchema1Manifest(object):
   def manifest_json(self):
     return self._parsed
 
+  @property
+  def manifest_dict(self):
+    return self._parsed
+
   @property
   def digest(self):
     return digest_tools.sha256_digest(self.payload)
@@ -252,6 +256,10 @@ class DockerSchema1Manifest(object):
   def checksums(self):
     return list({str(mdata.digest) for mdata in self.layers})
 
+  @property
+  def leaf_layer_v1_image_id(self):
+    return self.layers[-1].v1_metadata.image_id
+
   @property
   def leaf_layer(self):
     return self.layers[-1]
@@ -262,6 +270,10 @@ class DockerSchema1Manifest(object):
       self._layers = list(self._generate_layers())
     return self._layers
 
+  @property
+  def blob_digests(self):
+    return [str(layer.digest) for layer in self.layers]
+
   def _generate_layers(self):
     """
     Returns a generator of objects that have the blobSum and v1Compatibility keys in them,