### What? Fixes an issue where CSV exports and the preview table displayed all fields of documents in hasMany monomorphic relationships instead of only their IDs. ### Why? This caused cluttered output and inconsistent CSV formats, since only IDs should be exported for hasMany monomorphic relationships. ### How? Added explicit `toCSV` handling for all relationship types in `getCustomFieldFunctions`, updated `flattenObject` to delegate to these handlers, and adjusted `getFlattenedFieldKeys` to generate the correct headers.