Proc-macro derives for [`openpit`](https://crates.io/crates/openpit).
This crate provides the `RequestFields` derive macro used by the public
`openpit` `derive` feature.
End users normally depend on `openpit` and enable:
```toml
openpit = { version = "0.2", features = ["derive"] }
```
The derive macro is re-exported by `openpit`, so direct dependency on
`openpit-derive` is usually unnecessary.