Have a retrospective debug mode for prod admin use

[brendanheywood]

While testing you can turn on debug mode and login and see exactly what factors fired for you.

But it would be good to have some capability to do that kind of thing for another person. Some ideas:

1. have a look at the mfa history and attempt to reconstruct what did happen, this might be difficult / unviable

2. have a simple mode which isn't an exact history of what they did do, but is more a simulator of what they could do. ie in the 'Summary of good conditions for login' have a way of running that same logic in the context of a specific user. If will not be able to show the outcome of factors that require input, like totp or iprange, but it will be able to show the outcome of factors such as admin, capability, and also rule out input factors like totp if we can see they haven't even set it up yet. In particular we want to see if things like the grace mode will happen or not