Testing and support for 2D fields in X-Z and Y-Z, and 1D fields in X, Y, or Z

[VeckoTheGecko]

#2048 introduced an API that allows the grid to naturally extend towards structured grids of different dimensionality (2D where there isn't a X or isn't a Y direction, or 1D grids).

Having testing for these grids would be really beneficial so that we can:

• a) ensure native support for this - and so that our assertions on initialisation are compatible
• b) document how these grids can be constructed

[erikvansebille]

Good idea! I'd be happy to work on this in the coming days. Where should I put these test cases?

[VeckoTheGecko]

Awesome 🤩

Where should I put these test cases?

Below test_invalid_lon_lat in tests/v4/test_xgrid.py

[VeckoTheGecko]

cc @jimena-medinarubio - was running into difficulties getting 2D advection to work in XY space. Currently just setting to work with 2 depth slices at the surface