code: public void addJobChainLink (final JobKey firstJob, final JobKey secondJob)
    {
      ValueEnforcer.notNull (firstJob, "FirstJob");
      ValueEnforcer.notNull (firstJob.getName (), "FirstJob.Name");
      ValueEnforcer.notNull (secondJob, "SecondJob");
      ValueEnforcer.notNull (secondJob.getName (), "SecondJob.Name");
  
      m_aChainLinks.put (firstJob, secondJob);
    }
docs: Add a chain mapping - when the Job identified by the first key completes
  the job identified by the second key will be triggered.
  
  @param firstJob
  a JobKey with the name and group of the first job
  @param secondJob
  a JobKey with the name and group of the follow-up job