I've seen previously that it isn't possible (from about 4-5 months ago), but I'm looking to see if it's on the roadmap. I've been doing quite a bit of devcontainer development these days, and like to keep my db in a separate container. I'm guessing something similar to the prod connection string is in the works but not documented? e.g.
Weird, I guess the markdown parser didn't like connection string info there, I've wrapped it in a code block.
I think your markdown has a syntax error :)