Consider making assign_airzone and airzone_metric work on new caaqs object

I think there's a potential workflow where airzone info is added back into the full caaqs object, then airzone_metric works on that - the nice thing about that is that you don't have to specify all the column names etc, because they are standardized

Start by reading the existing assign_airzone and airzone_metric functions and examining the caaqs object structure. Determine whether airzone information can be added back to the full caaqs object while preserving standardized columns. Done means the functions work with the new caaqs object without requiring users to specify all column names.

Written by the indexing model from the issue text.