Lifetime issues with `<airup_sdk::nonblocking::Connection as airup_sdk::Connection>::invoke`

[sisungo]

It's hard to use the following pattern with current implementation due to lifetime issues:

async fn with_connection<T, F: Future<Output = Result<T, airup_sdk::ipc::Error>>>(
    &self,
    f: impl FnOnce(&mut Connection) -> F,
) {
    /* ... */
}

self.with_connection(|conn| conn.trigger_event(&event)).await;

The plan is:

• When async keyword generics is added to Rust, current emulation is rewritten.
• When related unstable features are stabilized, use unboxed futures to replace boxed ones.
• Fix the issue.

[sisungo]

Priority: Low-Medium.