Improve documentation and exception checking around functor gap models

GiudGiud commented 2 years ago

Bug Description

We just had a user try gap radiation with FV and they made the following mistakes:

used the non functor versions
did not ghost the higher D elements and got ghosting errors

We need to document the finite volume path from the main pages (eg the constraint ones and maybe the FE page) and possibly force finite volume users to use the functor version (even though they only loose second order accuracy if they dont)

Steps to Reproduce

From fv_modular_gap_heat_transfer_mortar_radiation_conduction.i test, remove ghosting to get an error and change the gap flux models to loose second order

Impact

Better user experience

lindsayad commented 2 years ago

I wouldn't put this in an FY21 project

GiudGiud commented 2 years ago

Should we have a FY22 TH project? Would it be common layer for maintenance of FV ?

lindsayad commented 2 years ago

We have an FY23 project for the common layer. I think this is valid to put in the common layer

idaholab / moose