Parse CRS if present

[Huite]

There are multiple ways to represent these (grid_mapping, etc, see also OGC conventions). Since the Ugrid topologies contain these, would be nice to use these if possible.

[Huite]

The easiest way to identify this is via grid_mapping_name as far as I can tell. Best to check cf-xarray and rioxarray.

[veenstrajelmer]

The required attributes for dflowfm are EPSG_code or epsg and grid_mapping_name (latitude_longitude in case of wgs84, otherwise not present or Unknown projected). QGIS also requires EPSG_code or epsg attributes for it to read the crs from the file. I suggest to also use these two attributes in the xugrid code.

This is also relevant when generating a grid with meshkernel and writing it to a netcdf file with xugrid, currently the attribute has to be set manually to the dataset.

Also relevant for .ugrid.to_crs() since it would help if the crs variable attrs is also adjusted and not only the node_x/node_y variables.

One more thought: grid_mapping_name seems to only be part of the crs if it is geographic, does not exist for projected crs. In dfm_tools I did a quick and dirty implementation of parsing the crs from FM model files in Deltares/dfm_tools#684