[keelerm84]

Summary

The FDv1 polling, streaming and file data sources (sync and async) no longer fall back to writing straight to the feature store when config.data_source_update_sink is None. The fallback skipped data source status updates and flag change events. The FDv1 data systems always set the sink before they build a data source, so each data source now reads the sink once at construction and raises ValueError if it is missing.

This also removes the unused LDClient._make_update_processor, which the FDv1 data system replaced.

---

Note

Overview
FDv1 polling, streaming, and file data sources (sync and async) no longer fall back to writing directly to the feature store when config.data_source_update_sink is missing. That fallback bypassed data-source status updates and flag-change notifications. Each source now resolves the sink once at construction via require_update_sink, which raises ValueError if it is unset; successful paths always call init, upsert, delete, and update_status on the sink without optional checks.

LDClient._make_update_processor is removed; update-processor selection stays on FDv1._make_update_processor (and the async data system equivalent), which always attaches the sink to the config before building a processor.

Tests use with_update_sink / with_async_update_sink to mirror production wiring, plus constructor tests that assert the new failure mode.

^{Reviewed by Cursor Bugbot for commit 8d2f493. Bugbot is set up for automated code reviews on this repo. Configure here.}