Unified user representation for web and API calls

Both approaches now use a pillar.auth.UserClass instance. g.current_user
is now always set to that instance, even for web entry points.

This UserClass instance can still be keyed like the old dict, but this is
for temporary compatibility and shouldn't be relied on in new or touched
code.

tests/test_api/test_blender_id_subclient.py

@@ -71,7 +71,7 @@ class BlenderIdSubclientTest(AbstractPillarTest):
         with self.app.test_request_context(headers={'Authorization': auth_header}):
             self.assertTrue(auth.validate_token())
             self.assertIsNotNone(g.current_user)
-            self.assertEqual(db_user['_id'], g.current_user['user_id'])
+            self.assertEqual(db_user['_id'], g.current_user.user_id)
 
     def _common_user_test(self, expected_status_code, scst=TEST_SUBCLIENT_TOKEN,
                           expected_full_name=TEST_FULL_NAME,