How to enable an automatic purge of temp files in Ubuntu 18.04

One privacy feature found in GNOME is the ability to setup the automatic purging of Trash and Temporary files. At first glance, you might not think think this much of a privacy-centric feature. Consider this: What files are collected in your Trash and what temporary files remain on your computer? And do you regularly reboot your machine to clear the /tmp directory (some distributions only clear /tmp on reboot)? Remember, the /tmp directory houses temporary files from applications. If you’re unsure what /tmp does: