add boilerplate for verbs data interface

data/interfaces/verbs.py

@@ -0,0 +1,18 @@
+class VerbsDataInterface(object):
+  """
+  Interface that represents all data store interactions required by the registry's custom HTTP
+  verbs.
+  """
+  @classmethod
+  def repository_is_public(cls, namespace_name, repo_name):
+    """
+    Returns a boolean for whether the repository with the given name and namespace is public.
+    """
+    raise NotImplementedError()
+
+
+class PreOCIModel(VerbsDataInterface):
+  """
+  PreOCIModel implements the data model for the registry's custom HTTP verbs using a database schema
+  before it was changed to support the OCI specification.
+  """

endpoints/verbs.py

@@ -31,8 +31,9 @@ logger = logging.getLogger(__name__)
 
 def _open_stream(formatter, namespace, repository, tag, synthetic_image_id, image_json, repo_image,
                  handlers):
-  """ This method generates a stream of data which will be replicated and read from the queue files.
+  """
-      This method runs in a separate process.
+  This method generates a stream of data which will be replicated and read from the queue files.
+  This method runs in a separate process.
   """
   # For performance reasons, we load the full image list here, cache it, then disconnect from
   # the database.