@UnstableApi
    default CompletableFuture<Void> initiateConnectionShutdown(Duration drainDuration) {
        requireNonNull(drainDuration, "drainDuration");
        return initiateConnectionShutdown(TimeUnit.NANOSECONDS.toMicros(drainDuration.toNanos()));
    }
Initiates graceful connection shutdown with a given drain duration and returns {@link CompletableFuture}
that completes when the connection associated with this context is closed.

@see #initiateConnectionShutdown()
@see #initiateConnectionShutdown(long)
core/src/main/java/com/linecorp/armeria/server/ServiceRequestContext.java