A description of the context in which an error occurred. This data
should be provided by the application when reporting an error, unless
the error report has been generated automatically from Google App Engine
logs.
The user who caused or was affected by the crash. This can be
a user ID, an email address, or an arbitrary token that
uniquely identifies the user. When sending an error report,
leave this field empty if the user was not logged in. In this
case the Error Reporting system will use other data, such as
remote IP address, to distinguish affected users. See
affected_users_count in ErrorGroupStats.
