GitLab

This flow is using attestation-based flow, but provides extra
EnrollmentToken along with Register request.

TBR: alemate@chromium.org
Bug: 854101
Change-Id: I9a0710dcffc7a2f68fe43097a9e0d321769ddf35
Reviewed-on: https://chromium-review.googlesource.com/c/1327211
Commit-Queue: Denis Kuznetsov <antrim@chromium.org>
Reviewed-by: Jesse Doherty <jwd@chromium.org>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#610171}