Macro quorum 

macro_rules! quorum {
    ($required:expr, $($future:expr),+ $(,)?) => { ... };
}

Waits for N of M futures to complete successfully.

Useful for consensus patterns where you need a majority to agree.

Semantics

let (successes, failures) = quorum!(2 of 3;
    replica_1(),
    replica_2(),
    replica_3(),
).await;

• Returns when required futures have completed successfully
• Remaining futures are cancelled after quorum is met
• If quorum cannot be met (too many failures), returns early with error