Modified routing_product.py to correctly set the river length to zero and set default values for reach attributes in sub-basins with no channel routing (i.e., sub-basins with lakes or headwater basins).

Modified routing_product.py to correctly set the river length to zero and set default values for reach attributes in sub-basins with no channel routing (i.e., sub-basins with lakes or headwater basins).

Co-authored-by: David Huard <huard.david@ouranos.ca>

…RavenPy into routing-product-fixes

Added a note in the CHANGELOG.rst, added contributor information in the .zenodo.json and in the AUTHORS.rst files, and added tests in the test_extractor.py script to confirm that everything is working as I expect.

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