foo.rs

#[post("/users", data = "<new_user>", format = "application/json")]
fn create(db: State<Db>, new_user: JSON<NewUser>) -> EndpointResult<JSON<User>> {
    let conn = &*db.pool().get()?;

    let new_user = NewUserReadyForInsertion::from(new_user.0);
    let user = diesel::insert(&new_user).into(users::table)
        .get_result::<User>(conn)?;

    Ok(JSON(user))
}