user defined metadata - spatial

[mo-marqh]

Demonstration of user customised metadata from XIOS

This includes spatial coordinate reference system metadata definitions.

[EdHone]

I've checked out the PR and run all the tests successfully, including the new test. I broke the new test a few times to test it's behaviour and everything seemed to behave properly.

I'm interested to see if similar behaviour can be achieved with the Fortran API as well - I might look into this in a future issue!

I believe the name of the python test test_resample_case.py should probably be renamed to something more appropriate. (Likewise with the class name/functions)

Technically I think the copywrite notice in the fortran program file should be changed to the year 2025, but I'm happy to overlook this as the code was probably written in 2024!

[mo-marqh]

thanks @EdHone , there was some unhelpful naming here, which i have hopefully improved with the latest commit

[EdHone]

Thanks, Mark. I'm happy with the changes you've made and I've tested the PR again and everything is working just as well as before. Happy to squash and merge now