Enforce initialization of state.ρ as aux.ref_state.ρ in Anelastic1D model.

[ilopezgp]

Description

The validity of the Anelatic1D model right now relies on the user initializing state.ρ=aux.ref_state.ρ. We should have this initialization as default, and output a warning message if this initialization is overwritten.

[charleskawczynski]

I'm not sure I understand the issue. state.ρ=aux.ref_state.ρ in the model seems like the right place for what we're doing. I think we can add a test at the end of the drivers to make sure that the final state.ρ is equal to the final aux.ref_state.ρ, otherwise, there are many places where the density could be modified (not just initialization).

[ilopezgp]

Ok, a test for this seems fine. Could we add a callback that checks state.ρ≈aux.ref_state.ρ point wise?

[charleskawczynski]

Yes, that seems fine