I'm trying to figure out the best way to handle "custom object" properties that will have arbitrary key and value pairs when using the Meltano SDK. I defined the property in the stream like this

Property('custom_fields', ObjectType(additional_properties=True))

but then when it runs it just complains that all the sub-properties are not found in the catalog and there's no way to include them. Do I have to dynamically retrieve the list of possible keys and include it in the schema, or is there a way to tell the SDK that this is just an object and to store it as an JSON object without a set schema?