Literally that. The actual RDS ui (aws or gcp). I can setup a new db instance in 3 clicks. Slap in the dbs ip into the container.
Granted even with one container and a single DB I found terraform useful as I don't have to fiddle with whatever DB, container, etc. settings there are every time. I also prefer to not have to memorize or figure out a UI I use once every other month. Too many UIs across too many things.