as-user header.
In this situation the user ID is the Box identifier for a user. User IDs can be
found for any user via the
GET /users endpoint, which is only available to
admins, or by calling the GET /users/me endpoint with an authenticated user session.Preconditions
Using theas-user header has a few requirements. Firstly, the application
needs to be configured to perform actions as users in the Developer
Console.

