code: function registerParticipant (name, participant) {
    let barrier = barriers[name];
  
    if (!barrier) {
      debug (`creating barrier ${name}`);
      barrier = barriers[name] = new Barrier ({name});
    }
  
    debug (`registering participant with barrier ${name}`);
    return barrier.registerParticipant (participant);
  }
docs: Factory method for registering a participant with a barrier. If the barrier
  does not exist, then a new barrier is created.
  
  @param name              Name of the barrier
  @param participant       JavaScript object
  @returns {Barrier}