Return 503 when deploy page is up
Follow up to !540 (merged)
It would be nice if we could return 503 when deploy page is up. This will signal to bots that this is temporary and they should not index. Also, it indicates to users (especially those interacting with our API) that everything is not '200 OK'.
Nginx won't make this easy. With try_files there doesn't seem to be a way to specify a different return code at a specific location. We can maybe find a way to do it, though.
This is a nice to have.