typesafe config substitution for relative paths

Question

Is there a way to use relative paths in substitution instead of absolute ones? I want to write this, which doesn't work:

service {
  password = "qwerty"
  url = "http://example.com?user=John&password="${password}
}

Works only this case:

service {
  password = "qwerty"
  url = "http://example.com?user=John&password="${service.password}
}