message: Add cancel calibration.
diff: @@ -169,6 +169,14 @@ public:
  return grpc::Status::OK;
  }
  + grpc::Status Cancel(grpc::ServerContext * /* context */,
  + const rpc::calibration::CancelCalibrationRequest * /* request */,
  + rpc::calibration::CancelCalibrationResponse * /* response*/) override
  + {
  + _calibration.cancel_calibration();
  + return grpc::Status::OK;
  + }
  +
  private:
  Calibration &_calibration;
  std::mutex _subscribe_mutex{};
  