Add optional support to fit to count data with CFR/IFR correction

[seabbs]

Allows tracking of for example severity over time.

[sbfnk]

If what you're thinking to have a time-varying (with some smoothing) scaling factor (and possibly delay, though may run into identifiability issues again)? Very much agree that this would be a great addition.

[seabbs]

yes and I don't think it will as long as the delay distribution is not time-varying or at least not time-varying on the same length scale as the scaling factor (as in the CFR work).