The existing Container Tabs extension gets you most of the way there. There's a little button (near the address bar? not at my desk so I can't check) to "always

The existing Container Tabs extension gets you most of the way there. There's a little button (near the address bar? not at my desk so I can't check) to "always open this site in this container". I just use the default containers that it comes with (plus the Facebook- and Google-specific container extensions) and assign certain sites to automatically open in a specific container.