code: public Usage postSubscriptionUsage(final String subscriptionCode, final String addOnCode, final Usage usage) {
          return doPOST(Subscription.SUBSCRIPTION_RESOURCE +
                          "/" +
                          subscriptionCode +
                          AddOn.ADDONS_RESOURCE +
                          "/" +
                          addOnCode +
                          Usage.USAGE_RESOURCE,
                  usage, Usage.class);
      }
docs: Post usage to subscription
  <p>
  
  @param subscriptionCode The recurly id of the {@link Subscription }
  @param addOnCode recurly id of {@link AddOn}
  @param usage the usage to post on recurly
  @return the {@link Usage} object as identified by the passed in object