Add a unique_key fields to the auth context type for tracking different instances

This will allow us to lookup a cache for the catalog without needing to make a database call

auth/auth_context_type.py

@@ -1,8 +1,7 @@
 import logging
 
-from cachetools import lru_cache
-
 from abc import ABCMeta, abstractmethod
+from cachetools import lru_cache
 from six import add_metaclass
 
 from app import app
@@ -90,6 +89,17 @@ class AuthContext(object):
     """
     pass
 
+  @property
+  @abstractmethod
+  def unique_key(self):
+    """ Returns a key that is unique to this auth context type and its data. For example, an
+        instance of the auth context type for the user might be a string of the form
+        `user-{user-uuid}`. Callers should treat this key as opaque and not rely on the contents
+        for anything besides uniqueness. This is typically used by callers when they'd like to
+        check cache but not hit the database to get a fully validated auth context.
+    """
+    pass
+
 
 class ValidatedAuthContext(AuthContext):
   """ ValidatedAuthContext represents the loaded, authenticated and validated auth information
@@ -213,6 +223,11 @@ class ValidatedAuthContext(AuthContext):
     if self.identity:
       identity_changed.send(app, identity=self.identity)
 
+  @property
+  def unique_key(self):
+    signed_dict = self.to_signed_dict()
+    return '%s-%s' % (signed_dict['entity_kind'], signed_dict.get('entity_reference', '(anon)'))
+
   def to_signed_dict(self):
     """ Serializes the auth context into a dictionary suitable for inclusion in a JWT or other
         form of signed serialization.
@@ -274,6 +289,15 @@ class SignedAuthContext(AuthContext):
     self.signed_data = signed_data
     self.v1_dict_format = v1_dict_format
 
+  @property
+  def unique_key(self):
+    if self.v1_dict_format:
+      # Since V1 data format is verbose, just use the validated version to get the key.
+      return self._get_validated().unique_key
+
+    signed_dict = self.signed_data
+    return '%s-%s' % (signed_dict['entity_kind'], signed_dict.get('entity_reference', '(anon)'))
+
   @classmethod
   def build_from_signed_dict(cls, dict_data, v1_dict_format=False):
     if not v1_dict_format:

auth/test/test_auth_context_type.py

@@ -26,6 +26,7 @@ def test_signed_auth_context(kind, entity_reference, loader, v1_dict_format, ini
     assert not validated.is_anonymous
 
   assert validated.entity_kind == kind
+  assert validated.unique_key
 
   signed = SignedAuthContext.build_from_signed_dict(validated.to_signed_dict(),
                                                     v1_dict_format=v1_dict_format)
@@ -36,6 +37,7 @@ def test_signed_auth_context(kind, entity_reference, loader, v1_dict_format, ini
     assert signed.description == validated.description
     assert signed.credential_username == validated.credential_username
     assert signed.analytics_id_and_public_metadata() == validated.analytics_id_and_public_metadata()
+    assert signed.unique_key == validated.unique_key
 
   assert signed.is_anonymous == validated.is_anonymous
   assert signed.authed_user == validated.authed_user