code: func (mc MongoClient) AddRegistration(r contract.Registration) (string, error) {
  	s := mc.getSessionCopy()
  	defer s.Close()
  
  	var mapped models.Registration
  	id, err := mapped.FromContract(r)
  	if err != nil {
  		return "", err
  	}
  
  	mapped.TimestampForAdd()
  
  	if err = s.DB(mc.database.Name).C(db.ExportCollection).Insert(mapped); err != nil {
  		return "", errorMap(err)
  	}
  	return id, nil
  }
docs: // Add a new registration
  // UnexpectedError - failed to add to database