Refactor auth code to be cleaner and more extensible

We move all the auth handling, serialization and deserialization into a new AuthContext interface, and then standardize a registration model for handling of specific auth context types (user, robot, token, etc).

auth/test/test_validateresult.py

@@ -1,45 +1,40 @@
 import pytest
 
-from auth.auth_context import (
-  get_authenticated_user, get_grant_context, get_validated_token, get_validated_oauth_token)
+from auth.auth_context import get_authenticated_context
 from auth.validateresult import AuthKind, ValidateResult
 from data import model
 from test.fixtures import *
 
-
 def get_user():
   return model.user.get_user('devtable')
 
+def get_app_specific_token():
+  return model.appspecifictoken.access_valid_token('test')
 
 def get_robot():
   robot, _ = model.user.create_robot('somebot', get_user())
   return robot
 
-
 def get_token():
   return model.token.create_delegate_token('devtable', 'simple', 'sometoken')
 
-
 def get_oauthtoken():
   user = model.user.get_user('devtable')
   return list(model.oauth.list_access_tokens_for_user(user))[0]
 
-
 def get_signeddata():
   return {'grants': {'a': 'b'}, 'user_context': {'c': 'd'}}
 
-
 @pytest.mark.parametrize('get_entity,entity_kind', [
   (get_user, 'user'),
   (get_robot, 'robot'),
   (get_token, 'token'),
   (get_oauthtoken, 'oauthtoken'),
-  (get_signeddata, 'signed_data'),])
+  (get_signeddata, 'signed_data'),
+  (get_app_specific_token, 'appspecifictoken'),
+])
 def test_apply_context(get_entity, entity_kind, app):
-  assert get_authenticated_user() is None
-  assert get_validated_token() is None
-  assert get_validated_oauth_token() is None
-  assert get_grant_context() is None
+  assert get_authenticated_context() is None
 
   entity = get_entity()
   args = {}
@@ -52,16 +47,16 @@ def test_apply_context(get_entity, entity_kind, app):
   if entity_kind == 'oauthtoken':
     expected_user = entity.authorized_user
 
+  if entity_kind == 'appspecifictoken':
+    expected_user = entity.user
+
   expected_token = entity if entity_kind == 'token' else None
   expected_oauth = entity if entity_kind == 'oauthtoken' else None
+  expected_appspecifictoken = entity if entity_kind == 'appspecifictoken' else None
+  expected_grant = entity if entity_kind == 'signed_data' else None
 
-  fake_grant = {
-    'user': {
-      'c': 'd'},
-    'kind': 'user',}
-  expected_grant = fake_grant if entity_kind == 'signed_data' else None
-
-  assert get_authenticated_user() == expected_user
-  assert get_validated_token() == expected_token
-  assert get_validated_oauth_token() == expected_oauth
-  assert get_grant_context() == expected_grant
+  assert get_authenticated_context().authed_user == expected_user
+  assert get_authenticated_context().token == expected_token
+  assert get_authenticated_context().oauthtoken == expected_oauth
+  assert get_authenticated_context().appspecifictoken == expected_appspecifictoken
+  assert get_authenticated_context().signed_data == expected_grant