Allow Variable metadata to inherit from the grid

[VeckoTheGecko]

This is related to handling cartesian/spherical shell meshes in Parcels (and distinguishing between them during runtime for unit conversion and (in this case) output metadata)

Allowing users to specify this on the Variable level would allow them to add custom variables with correct units/metadata based on the grid.

---

@erikvansebille Erik van Sebille 20 hours ago
The units here are degrees_north when the grid._mesh="spherical", otherwise they are in meters. It would be good to make that distinction here already!

Member
Author
@VeckoTheGecko VeckoTheGecko 20 hours ago
I think this would need to inherit from the grid - similar to what we do for _SAME_AS_FIELDSET_TIME_INTERVAL. Would that be a good solution?

Member
@erikvansebille Erik van Sebille 19 hours ago
Yep indeed; that is what I proposed (but maybe wasn't clear enough)

Member
Author
@VeckoTheGecko VeckoTheGecko now
Yes, I was mainly thinking through implementation details (i.e., keeping it on the Variable level so that users can also have their custom variables also inherit from the grid). I think that this would be good to have in a future PR
Originally posted by @VeckoTheGecko in #2142 (comment)