Support older xarray versions or require minimal xarray version

[veenstrajelmer]

Due to some compatibility issues that were reported by users, I deep dove into dfm_tools minimal requirements. There was one where xugrid popped up. With xarray<=2022.10.0 I get this ImportError:

ImportError while importing test module 'c:\DATA\dfm_tools\tests\test_xugrid_helpers.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\importlib\__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests\test_xugrid_helpers.py:10: in <module>
    import xugrid as xu
C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\site-packages\xugrid\__init__.py:15: in <module>
    from xugrid.core.dataarray_accessor import UgridDataArrayAccessor
C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\site-packages\xugrid\core\dataarray_accessor.py:11: in <module>
    from xugrid.plot.plot import _PlotMethods
C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\site-packages\xugrid\plot\__init__.py:1: in <module>
    from xugrid.plot.plot import (
C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\site-packages\xugrid\plot\plot.py:9: in <module>
    from xugrid.plot.utils import (
C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\site-packages\xugrid\plot\utils.py:31: in <module>
    from xarray.core.utils import is_scalar, module_available
E   ImportError: cannot import name 'module_available' from 'xarray.core.utils' (C:\Users\veenstra\Anaconda3\envs\dfm_tools_env\lib\site-packages\xarray\core\utils.py)

It is fine to not support these older versions (xarray>=2022.11.0 work), but in that case it should be documented in the xugrid package requirements so it automatically updates xarray if needed.

[veenstrajelmer]

This is already solved in the main branch, so I will close this issue again. I have now tested with xarray 2022.6.0, so over a year old, and it works fine.