document handling of large vector data

[jdries]

Add documentation to openeo python client for working with large vector dataset.

Partial code example of working with larger vector dataset:

    parcels = con.vectorcube_from_paths(["https://artifactory.vgt.vito.be/testdata-public/parcels/32TPT.pq"],format="parquet")
    dates = {'start': '2021-05-01', 'end': '2021-06-01'}
    cube = datacube_s1.filter_temporal(
        start_date=date_shift(dates['start'], unit="day", value=-90),
        end_date=date_shift(dates['end'], unit="day", value=90)) \
        .aggregate_spatial(geometries=parcels,
                           reducer=lambda x: array_create([mean(x)]))

    cube.download("S1_32TPT.csv")

Key elements to include in docs:

• When a user tries to run something with too much data, the 'POST' request becomes to large, and a 'request entity too large' error happens
• To avoid this, vector data should be uploaded to a public location, and referenced by url. (This can be something like google drive normally.)
• As an extra, using a more efficient file format, like parquet, is recommended, as geojsons can get very large.

[jdries]

Hitting this issue with geoparquet files:

Traceback
 (most recent call last):
  File "/opt/venv/lib64/python3.8/site-packages/flask/app.py", line 
1516, in full_dispatch_request
    rv = self.dispatch_request()
  File "/opt/venv/lib64/python3.8/site-packages/flask/app.py", line 
1502, in dispatch_request
    return 
self.ensure_sync(self.view_functions[rule.endpoint])(**req.view_args)
  File 
"/opt/venv/lib64/python3.8/site-packages/openeo_driver/users/auth.py", 
line 88, in decorated
    return f(*args, **kwargs)
  File "/opt/venv/lib64/python3.8/site-packages/openeo_driver/views.py",
 line 840, in queue_job
    backend_implementation.batch_jobs.start_job(job_id=job_id, 
user=user)
  File 
"/opt/venv/lib64/python3.8/site-packages/openeogeotrellis/backend.py", 
line 1240, in start_job
    self._start_job(job_id, user.user_id, _get_vault_token)
  File 
"/opt/venv/lib64/python3.8/site-packages/openeogeotrellis/backend.py", 
line 1270, in _start_job
    and 
self._scheduled_sentinelhub_batch_processes(spec['process_graph'], 
api_version, registry,
  File 
"/opt/venv/lib64/python3.8/site-packages/openeogeotrellis/backend.py", 
line 1777, in _scheduled_sentinelhub_batch_processes
    projected_polygons = to_projected_polygons(self._jvm, 
geometry=geometries, crs=crs, buffer_points=True)
  File 
"/opt/venv/lib64/python3.8/site-packages/openeogeotrellis/utils.py", 
line 226, in to_projected_polygons
    raise RuntimeError(f"Unexpected crs: {crs!r} != {expected_crs!r}")
RuntimeError: Unexpected crs: 'EPSG:4326' != 'ogc:crs84'

[jdries]

Documentation added!