I am a bit confused about the basic difference between an Access Class and a Handler Class in SAP MDG. From what I can see the Handler class has almost all the functionalities such as mapping to staging areas, saving custom entities to custom tables, validations, derivations etc. Yet in a review comment we received a view that instead of using the handler class for saving custom entities we should use the access class. Can you please help me with the concept here? I will design it accordingly in future then.