Comment 3 for bug 1879545

I tweaked the proposed solution from comment 1. We don't make basic_auth.csv optional, but rather ensure it's a stubbed out file. I went this route because i thought it would be nicer if cluster operators could see that the file was still there with a clear message that it shouldn't be used for auth in 1.19+. Making it optional could have led to ops generating their own basic_auth.csv and wondering why those entries had no effect.