Add the username to the csv output in the MyLA event log data

[jennlove-um]

Describe your problem or feature you'd like added

The log files that are exported include a column called "user" - this data is the id from the auth_user table. To make this exported data more useful, it should also include the username, which would match the Canvas data. Administrators who use this data need to be able to connect MyLA users to Canvas users.

Describe the solution you'd like

Export the log file with 2 columns to identify the user:
user - the id from the auth_user table
username - the username from the auth_user table

[jennlove-um]

Testing passes in beta.