Interface ProjectActionParamValuesOptions

What becomes of an entity object whose entity the user may not read:

• 'null' (the default) replaces it with null, for a destination that would otherwise serialize the object's internal state, such as JSON.stringify.
• 'keep' returns it untouched, for a destination whose serializer already drops class instances (CopyScalarsAndArrays), so its output stays exactly what it was before entity objects were projected.