Unit tests emit quite a few warnings

[plamut]

It appears that recent additions resulted in several warning messages when running unit tests:

PytestUnknownMarkWarning: Unknown pytest.mark.enable_add_server_timeout_header - is this a typo?  You can register custom marks to avoid this warning - for details, see https://docs.pytest.org/en/stable/mark.html
    @pytest.mark.enable_add_server_timeout_header
...
FutureWarning: Assigning CRS to a GeoDataFrame without a geometry column is now deprecated and will not be supported in the future.
    return geopandas.GeoDataFrame(crs=_COORDINATE_REFERENCE_SYSTEM)
...
UserWarning: Geometry is in a geographic CRS. Results from 'area' are likely incorrect. Use 'GeoSeries.to_crs()' to re-project geometries to a projected CRS before this operation.

At least those that we have control over (e.g. user warnings) should be addressed to reduce the noise.