Produce an EmittedFile with the updated additionalSchemaInfo JSON.
Merge new soft FK entries into an existing config. Deduplicates — won't add the same FK twice.
Add soft PK entries for tables. Uses SoftPrimaryKeys from TableDefinition.
Parse existing additionalSchemaInfo JSON content. Returns empty object if content is empty/null.
Manages soft PK and FK definitions in the additionalSchemaInfo JSON file. Mirrors the integration schema-builder's SoftFKConfigEmitter but works with SchemaEngine's generic TableDefinition types.