[keelerm84]

Summary

The FDv2 backend does not support payload filtering, and the SDK already documents that payload_filter_key has no effect with the FDv2 data system and logs a warning when it is set. The FDv2 data sources still added the filter query parameter to their requests, though. They no longer do:

• The FDv2 streaming and polling data sources, sync and async, send no filter parameter.
• The FDv1 fallback polling requesters that the FDv2 data system uses also send no filter parameter. A fallback thus cannot change the client from the full data set to a filtered subset during a session.
• payload_filter_key is removed from the DataSourceBuilderConfig protocol, because only the FDv2 data sources read that protocol. Config and AsyncConfig keep the option for the FDv1 data system, and the FDv2 warning stays.
• The contract-test services no longer map dataSystem.payloadFilter. No version of the test harness sends that field. The filtering capability stays for the FDv1 tests.

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Note

Overview
Stops applying payload_filter_key on FDv2 data-system HTTP requests, aligning runtime behavior with the existing docs/warning that filtering does not apply to FDv2.

FDv2 streaming and polling requesters (sync and async) no longer add a filter query parameter; they still send basis when a selector is defined. FDv1 fallback polling used inside the FDv2 data system also omits filter, so an in-session fallback cannot shrink the payload to a filtered subset.

payload_filter_key is removed from the DataSourceBuilderConfig protocol (FDv2-only consumers). Config / AsyncConfig keep the option for the legacy FDv1 data path. Contract-test harnesses no longer wire dataSystem.payloadFilter into client opts.

Adds test_payload_filter.py to assert FDv2 sources never send filter even when config sets payload_filter_key.

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