AbstractHandlerServiceclass always performs the actions with the same handler whereas a service inheriting the
AbstractMultiHandlerServiceclass needs to be instructed which registered handler to use.
OutputtableInterfaceand using the
OutputHandlersTraitmentioned above will automagically call the
outputmethod of all its registered handlers also implementing the
OutputtableInterfacewhen the service's own
outputmethod is called. Pretty neat, huh?