CompletableFuture<Boolean> completableFuture() {
        return CompletableFutures.allOf(operands)
                .thenApply(ops -> ops.stream().allMatch(bool -> bool));
    }
<p>Adds a {@link CompletableFuture} to this conjunction. This can be called at any time, even after having called
{@link #get()} previously.</p>

@param operand The operand to add to this conjunction.
jdisc_core/src/main/java/com/yahoo/jdisc/handler/FutureConjunction.java