#3416 feat: JSONify variant types when flattening records Pull request opened by edgarrmondragon on <!date^1765844580^{date_short}|2025-12-16T00:23:00Z> Summary by Sourcery Coerce variant and typeless schema properties to JSON-serialized strings during flattening and ensure record flattening respects these markers. New Features: • Mark combined (oneOf/anyOf/allOf) and typeless schema properties with an x-json-serialize flag and coerce them to nullable string type when flattening schemas. Enhancements: • Update record flattening logic to JSON-encode values based on the x-json-serialize schema marker and to correctly use flattened property keys when deciding serialization. Tests: • Expand flattening tests to cover combinator schemas, edge cases, and JSON serialization behavior for both simple and complex values, including end-to-end scenarios. meltano/sdk