Description of problem: The auto-generated Author Group file is not a great way to handle legacy imported content. In many cases, the original authors of the material may be long since gone, might work in a completely different department, might be external to the company, or for any other reason not be someone who is or should be a registered CCMS user. Moreover, in the case of legacy content, we might have no easy way to determine who was responsible for what. 


Version-Release number of selected component (if applicable):
Current prod

How reproducible:
100%

Steps to Reproduce:
1. Try to specify an Author Group file

Actual results:
Discover that you can't

Expected results:
Treat Author Group like the custom Feedback and Legal Notice files

Additional info:
Workaround is to arbitrarily assign legacy writers to legacy content