code: public void deleteAddOn(final String planCode, final String addOnCode) {
          doDELETE(Plan.PLANS_RESOURCE +
                   "/" +
                   planCode +
                   AddOn.ADDONS_RESOURCE +
                   "/" +
                   addOnCode);
      }
docs: Deletes an {@link AddOn} for a Plan
  <p>
  
  @param planCode  The {@link Plan} object.
  @param addOnCode The {@link AddOn} object to delete.