dspace_statistics_api/app.py: Use bounded_stream in on_post

For reasons I don't quite understand, we need to use bounded_stream
in the on_post request handler in order to use simulate_post() with
the testing client in Falcon 2.0.0. Normal runtime operation via
gunicorn does not have any issues with stream.

See: https://github.com/falconry/falcon/issues/1720
See: https://github.com/falconry/falcon/issues/1554

dspace_statistics_api/app.py

@@ -66,7 +66,7 @@ class AllItemsResource:
         # Only attempt to read the POSTed request if its length is not 0 (or
         # rather, in the Python sense, if length is not a False-y value).
         if req.content_length:
-            doc = json.load(req.stream)
+            doc = json.load(req.bounded_stream)
         else:
             raise falcon.HTTPBadRequest(
                 title="Invalid request", description=f"Request body is empty."