func: function checkinSpeaker(uint256 _talkId)
          external
          onlyOwner
          duringEvent
      {
          require(speakersTalks[_talkId].checkedIn == false);
          require(speakersTalks[_talkId].status == ApplicationStatus.Accepted);
          
          uint256 bidId = totalSupply();
          super._mint(msg.sender, bidId);
          speakersTalks[_talkId].checkedIn = true;
      }