Can't seem to find any documentation but is it possible to add a secure service to agol/portal with gis.content.add()? Don't seem to have the option inside item_properties so I'm thinking this is not possible at the moment.
Or possible with the rest api?
It doesn't look like there are any keys to modify the sharing settings of items added using gis.content.add, but you can modify the share settings after the item is added using:
item.share(<share settings here>)