use warp::Filter;

...

async fn get_questions() -> Result<impl warp::Reply, warp::Rejection> { ➊
    let question = Question::new( ➋
        QuestionId::from_str("1").expect("No id provided"),
        "First Question".to_string(),
        "Content of question".to_string(),
        Some(vec!["faq".to_string()]),
    );

    Ok(warp::reply::json( ➌
        &question
    ))
}