Preserve empty URL query parameters

[biefan]

Summary

• preserve explicitly empty query parameter values when extracting URL params
• keep empty query parameters intact when make_request_and_raise_if_error_async() rebuilds request URLs
• add regression coverage for blank query values in both helper and request paths

Problem

extract_url_parameters() currently uses parse_qs() with its default behavior, which drops query parameters whose value is explicitly empty.

For example:

• https://api.example.com/endpoint?api-version=&mode=test
• http://testserver/api/test?alpha=&beta=1

currently lose the empty parameter before the request is rebuilt.

That means explicitly provided empty query parameters are silently removed from outgoing requests, which can change endpoint behavior for APIs that distinguish flag= from an absent parameter.

Testing

• .venv/bin/pytest tests/unit/common/test_common_net_utility.py -q