static Executor makeContextPropagating(Executor executor) {
        return PropagatingContextAwareExecutor.of(executor);
    }
Returns an {@link Executor} that will execute callbacks in the given {@code executor}, propagating
the caller's {@link RequestContext} (if any) into the callback execution.
If this executor is only used from a single request then it's better to use
{@link #makeContextAware(Executor)}
core/src/main/java/com/linecorp/armeria/common/RequestContext.java