The files table has an author field, which is often populated when files are imported from repositories (to record the original authorship)

1. Add a new column to the files entity to represent this value (column type = text); add tests (somehow I forgot I already added this some time ago, visible in the link below. Senior moment)
2. Add a new filter to the entity to represent this value (filter type = text); add tests

This will improve the files report source reporting, and pair well with the entity license data