如何在tera模板中使用rocket::response::Flash

[dependencies]
rocket = "0.5"
tera = "1.0"

use rocket::Response;
use rocket::response::Flash;
use rocket::request::FlashMessage;
use tera::{Context, Tera};

#[derive(Responder)]
pub struct FlashMessageResponder {
    flash: Option<FlashMessage<'static>>,
    response: Response<'static>,
}

#[get("/example")]
pub fn example(flash: Option<FlashMessage<'_>>) -> FlashMessageResponder {
    let tera = Tera::new("templates/**/*.html").unwrap();
    let mut context = Context::new();

    // 在上一个请求中设置Flash消息
    let flash_message = flash.map(|msg| {
        let mut ctx = Context::new();
        ctx.insert("message", msg.msg());
        ctx.insert("message_type", msg.name());
        ctx
    });

    // 将Flash消息绑定到模板上下文中
    if let Some(flash) = flash_message {
        context.extend(flash);
    }

    // 加载Tera模板并渲染
    let rendered = tera.render("example.html", &context).unwrap();

    // 创建FlashMessageResponder实例并返回
    FlashMessageResponder {
        flash,
        response: Response::builder()
            .header(ContentType::HTML)
            .sized_body(Cursor::new(rendered))
            .finalize(),
    }
}