Add Authorization header with token to user info call

While not required, it is recommended to send the token as an Authorization header to the UserInfo call in OIDC: http://openid.net/specs/openid-connect-core-1_0.html#UserInfo

Some implementations expect this and will fail if not present

oauth/base.py

@@ -101,7 +101,11 @@ class OAuthService(object):
       'alt': 'json',
     }
 
-    got_user = http_client.get(self.user_endpoint(), params=token_param)
+    headers = {
+      'Authorization': 'Bearer %s' % token,
+    }
+
+    got_user = http_client.get(self.user_endpoint(), params=token_param, headers=headers)
     if got_user.status_code // 100 != 2:
       raise OAuthGetUserInfoException('Non-2XX response code for user_info call: %s' %
                                       got_user.status_code)