New uid is not returned.

* **Version**: v0.1.43 / master

Hi ! I found a little bug: when changing headers on each request and making batch requests, updating the email of the current user ends in 401 Unauthorized because the uid (email) changed and the headers aren't returned (batch).

Start by reproducing a batch request that updates the current user's email while changing headers on each request, then trace where the response headers are assembled. Done means the updated uid is returned after the email change and the subsequent request no longer receives 401 Unauthorized.

Written by the indexing model from the issue text.