Conversion model to provide extinguish for composite models

[karllark]

If simultaneously fitting the stellar and extinction, it would be good to do this with a composite model.
For example, assume a blackbody for the stellar and one of the dust_extinction models. Need a way to have the extinguishing factors as a model so then the model to fit is just, for example (BlackBody1D | ExtFactor | CCM89).

[krislars]

I like this idea. I think it would make synthetic photometry more straightforward, I too.