CLC-1497 Another approach to multi-role test users: fake data overlays

JIRA: https://jira.media.berkeley.edu/jira/browse/CLC-1497

This is a second approach to supporting fake data in production-like test environments. I'd like the reviewer to carefully consider whether this is sustainable for the long term (or if there's a better way of augmenting real data sets with fake data for test purposes on calcentral-dev/qa).