It just makes Rswag specs look more different to other request specs and
I found that discouraging. It's good to know that the parameter is just
specified with `let` and that it works exactly in the same way as `let`
in other specs.
The downside is maybe that it's not obvious that those `let` statements
have to correspond with the parameters for the request but error
messages will tell you if you got it wrong. And there's also the
`parameter` declaration to make that clear.