This isn't quite foolproof; if, for example, I tried to make a request to "https://blah.com/foo" and `base_url` was "https://foo.com/blah" I'd end up with "https://foo.com/blahhttps://bla.com/foo".

However, this also isn't a bad compromise if you don't care about being rock-solid against that kind've mistake. I'd still do some handling to make sure there's a slash between the two components, though.