old_contents: // discard
  
  exports.register = function () {
      this.register_hook('queue','discard');
      this.register_hook('queue_outbound', 'discard');
  }
  
  exports.discard = function (next, connection) {
      var transaction = connection.transaction;
      if (connection.notes.discard || transaction.notes.discard) {
          connection.loginfo(this, 'discarding message');
          // Pretend we delivered the message
          return next(OK);
      }
      // Allow other queue plugins to deliver
      return next();
  }
  
new_contents: // discard
  
  exports.register = function () {
      this.register_hook('queue', 'discard');
      this.register_hook('queue_outbound', 'discard');
  }
  
  exports.discard = function (next, connection) {
      var transaction = connection.transaction;
      if (connection.notes.discard || transaction.notes.discard) {
          connection.loginfo(this, 'discarding message');
          // Pretend we delivered the message
          return next(OK);
      }
  
      if (process.env.YES_REALLY_DO_DISCARD) {
          return next(OK);
      }
  
      // Allow other queue plugins to deliver
      return next();
  }
  
subject: add ENV that permits discarding