#[derive(Debug)]
struct Question {
    id: QuestionId,
    title: String,
    content: String,
    tags: Option<Vec<String>>,
}

#[derive(Debug)]
struct QuestionId(String);

impl Question {
    fn new(
        id: QuestionId,
        title: String,
        content: String,
        tags: Option<Vec<String>>
    ) -> Self {
        Question {
            id,
            title,
            content,