UDP notebook finetuning

[soxofaan]

I recently gave a demo using https://documentation.dataspace.copernicus.eu/notebook-samples/openeo/UDP.html
and wanted to feedback some notes and improvements (I'm bit in hurry and can't do it as PR):

• import json is unused

• spatial_extent_param = Parameter(
      name="bbox",
      description="The bounding box to load.",
      schema={"type": "object", "subtype": "geojson"},
  )
  

  this is confusing: the parameter name is bbox, but the subtype is geojson. I think the name should be changed to "geometry" or the subtype should be changed to "bounding-box".

• connection.datacube_from_process... : also add a description, e.g. description="NDWI: Normalized Difference Water Index"