Control Firefox cookies with Cookie AutoDelete
From Firefox 57 onwards, Add-ons will stop working and be replaced with WebExtensions. One very used Add-on is Self-Destructing Cookies, but this extension will not be rewritten as a WebExtension. As a replacement you can use Cookie AutoDelete.
Install the WebExtension as normal, and configure Firefox and the Cookie AutoDelete WebExtension:
Firefox cookie settings
Cookie AutoDelete settings