Netcdf load ignores 'scale_factor_at_projection_origin' of Stereographic grib-mapping #3845
Description
The CF conventions state that ['scale_factor_at_projection_origin' is a required attribute for Stereographic grid-mapping
But our code is completely ignoring this.
( Note that the comment "this is checked elsewhere" is totally untrue ! It couldn't be really, as this is the only place that we will inspect the file variable )
By ignoring this, we are mis-representing any input where this is different from 1.0.
Suggested action:
We should either support this, or at least check it and raise an error/warning when our loaded version is incorrect.
Note also: when saving, we currently warn that the result is not exact + don't save anything.
We could fix that too, but at least it is not "wrong".