#3402 WIP: Load method strategies Pull request opened by edgarrmondragon on <!date^1764805717^{date_short}|2025-12-03T23:48:37Z> Summary by Sourcery Introduce pluggable SQL load strategies and loaders to support append-only, overwrite, and upsert load methods with backward-compatible behavior. New Features: • Add LoadMethodStrategy hierarchy and concrete append-only, overwrite, and upsert strategies for SQL sinks. • Introduce reusable Loader classes (simple insert, temp-table upsert, and merge-based upsert) for database-agnostic DML handling. • Expose load strategies and loaders from the sql package for easier customization by targets. Enhancements: • Wire SQLConnector and SQLSink to select and use load strategies based on configuration while preserving legacy table preparation as a fallback. • Enable SQLSink to delegate table preparation and batch loading to the selected load strategy, including config validation and capability checks. Tests: • Add comprehensive tests for load strategies, loaders, and factory selection behavior, including append-only, overwrite, upsert, and custom merge scenarios. • Update the dummy SQL connector used in sink tests to declare support for overwrite and merge-upsert load methods. meltano/sdk