Consistent application of vignetting with and without using RubinOptics

[jchiang87]

At #368 , Josh asks:

• Should we require input.vignetting if using a RubinOptics photon op?
• What happens if input.vignetting is populated and we're photon-shooting without RubinOptics? are the FFT and shoot objects still consistent in this case (i.e., does the vignetting affect the non-RubinOptics shoot objects?)

For the first question, Mike recommends we emit a warning if input.vignetting isn't populated. For the second, it seems we should apply the vignetting scaling to the non-RubinOptics shoot objects.

[cwwalter]

Jim, is this something that can wait until after 2.0? Or do we need to address it right away?

[jchiang87]

If we don't plan to run with RubinOptics disabled for any serious work (i.e., case 2 above), then I would say this can wait. Nevertheless, I may find time to work on it in the next week or so.