#3688 test: Cover more flattening cases Pull request opened by edgarrmondragon SSIA Summary by Sourcery Expand test coverage for schema and record flattening edge cases. Tests: • Add tests for flattening schemas without properties and handling duplicate flattened keys. • Add tests verifying key abbreviation behavior in schema and record flattening when max_key_length is enforced. • Adjust existing flatten_record test to use multi-line call formatting while preserving behavior. meltano/sdk