This should make it much easier to debug issues where a particular
user is hosing our API, for example.
(imported from commit cbea49fd1e11805cadf564bd9160d3d6bf7e0eca)
Previously we only got the user ID for /json requests, not /api
requests, and also only got the user ID, not the email address.
(imported from commit c3625f9c1a48430e35183be6c90a7855f3714948)