We have a notion of CoverageProvider (which performs some task on selected Identifiers) and WorkCoverageProvider (which performs some task on selected Works). We need a notion of ContributorCoverageProvider, which performs some task on selected Contributors, such as looking them up in VIAF or Library of Congress data.

This will let us keep track of who we've handled and who we haven't. If our VIAF processing rules ever change, we can wipe out the coverage records and start over again.