[Feature Request] add async_then_some

[cathaysia]

Can you add some function like this?

use std::future::Future;

pub trait AsyncThenSome {
    fn async_then_some<F>(self, future: F) -> impl Future<Output = Option<F::Output>> + Send
    where
        F: Future + Send,
        F::Output: Send;
}

impl AsyncThenSome for bool {
    async fn async_then_some<F>(self, future: F) -> Option<F::Output>
    where
        F: Future + Send,
        F::Output: Send,
    {
        if !self { None } else { Some(future.await) }
    }
}

pub trait AsyncMap<T> {
    fn async_map<F, R>(self, func: F) -> impl Future<Output = Option<R>>
    where
        F: AsyncFn(T) -> R;
}

impl<T> AsyncMap<T> for Option<T> {
    async fn async_map<F, R>(self, func: F) -> Option<R>
    where
        F: AsyncFn(T) -> R,
    {
        match self {
            None => None,
            Some(v) => Some(func(v).await),
        }
    }
}