warn for geographic crs input

[jGaboardi]

Following up from #369, it would be nice to implement @martinfleis' idea of throwing a warning when the CRS is geographic. Here is where that happens in geopandas.

What we need to decide is where/how this should happen in momepy, and which classes/functions it should happen inside. Maybe a utility function that can be dropped in; something that mimics check_geographic_crs() in GeometryArray:

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In [1]: import geopandas
   ...: from shapely.geometry import Point
   ...: import warnings
   ...: 
   ...: def warn_if_geographic(df):
   ...:     if df.crs and df.crs.is_geographic:
   ...:         warnings.warn(
   ...:             "Geometry is in a geographic CRS. Results are likely "
   ...:             "incorrect. Use 'GeoSeries.to_crs()' to re-project "
   ...:             "geometries to a projected CRS before this operation.",
   ...:             UserWarning
   ...:         )
   ...: 

In [2]: gdf = geopandas.GeoDataFrame(geometry=[Point(0,0)], crs="EPSG:4236")
   ...: warn_if_geographic(gdf)
<ipython-input-1-c0a117e90671>:7: UserWarning: Geometry is in a geographic CRS. Results are likely incorrect. Use 'GeoSeries.to_crs()' to re-project geometries to a projected CRS before this operation.
  warnings.warn(

In [3]: gdf = geopandas.GeoDataFrame(geometry=[Point(0,0)], crs="EPSG:3857")
   ...: warn_if_geographic(gdf)

In [4]: gdf = geopandas.GeoDataFrame(geometry=[Point(0,0)])
   ...: warn_if_geographic(gdf)

Or possibly using check_geographic_crs() directly?

[martinfleis]

Or possibly using check_geographic_crs() directly?

That is not public, rather not.

We can potentially have a decorator but it would decorate nearly everything :D.