Copyright filter under Files section not working consistently

Issue Type: Bug
Issue Description:

I've noticed that the search filter for the "Copyrights" column under _Files_ section does not actually appear to do anything.

When searching for either a partial copyright string (e.g. "XYZ") or the full string as it's listed under the _Licensed_ section (e.g. "Copyright (c) 2020 XYZ Inc." and clicking the green "Search" button, the page refreshes but the requested filters aren't applied.


I expect this feature would operate similar to the other filters in the Files section, where if you enter in your search string, the number of entries will be reduced to just those that match your search filter. This isn't happening for me here.

Furthermore, it might be a good improvement for the attributions to show as a "select" type filter like we see for filtering by License, rather than the plain text field. I can create a separate feature request for this if others agree it's a good idea.


Thanks.