code: public CompletableFuture<SubscriptionDescription> createSubscriptionAsync(SubscriptionDescription subscriptionDescription, RuleDescription defaultRule) {
          subscriptionDescription.defaultRule = defaultRule;
          return putSubscriptionAsync(subscriptionDescription, false);
      }
docs: Creates a new subscription in the service namespace with the provided default rule.
  See {@link SubscriptionDescription} for default values of subscription properties.
  @param subscriptionDescription - A {@link SubscriptionDescription} object describing the attributes with which the new subscription will be created.
  @param defaultRule - A {@link RuleDescription} object describing the default rule. If null, then pass-through filter will be created.
  @return {@link SubscriptionDescription} of the newly created subscription.