When I want to add board shape to final output in output job, I draw board shape on a useless layer and then I add that layer to output job.
Is it possible to add board shape automatically in Altium Designer?
Unfortunately that isn't possible. As far as I know the industry-accepted standard (et least here in Europe it's pretty clear) is to use Mechanical 1 for the board outline. Mechanical 1 will contain the board outline, including possible cutouts but nothing else. Provide that to your PCB manufacturer and you should be fine.