It is possible to method to inject a credit card applicatoin level username or id (within this situation, the django username or id) in to the Apache or ngnix log? Observe that I am not asking concerning the HTTP auth username.

We all do something similar to this, only we tell Apache to keep the the Django sessionid cookie.

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\" %{sessionid}C" withsession
CustomLog logs/ withsession

It's kind of a 2-step process to map the sessionid towards the user, but it's not hard to implement. You could do this such like by setting a cookie using the explicit ID inside it after which while using custom log to capture it.