code: public Builder addProcessors(int index, Processor... processors) {
          while (index >= this.processors.size()) {
              this.processors.add(new ArrayList<>());
          }
          this.processors.get(index).addAll(new ArrayList<>(Arrays.asList(processors)));
          return self();
      }
docs: Add a set of processors to handle an outgoing exchange at a particular offset (n'th message)
  
  @param index      The exchange offset that these processors should be applied to
  @param processors The processors that will handle populating the exchange with an appropriate outgoing value