Applies or update a watermark on a file.
The access token received from the authorization server in the OAuth 2.0 flow.
The unique identifier that represents a file.
The ID for any file can be determined
by visiting a file in the web application
and copying the ID from the URL. For example,
for the URL https://*.app.box.com/files/123
the file_id is 123.
The watermark to imprint on the file.
Returns an updated watermark if a watermark already existed on this file.
A watermark is a semi-transparent overlay on an embedded file preview that displays a viewer's email address or user ID and the time of access over a file's content.