code: func (mc MongoClient) UpdateEvent(e contract.Event) error {
  	var mapped models.Event
  	id, err := mapped.FromContract(e, mc)
  	if err != nil {
  		return err
  	}
  
  	mapped.TimestampForUpdate()
  
  	return mc.updateId(db.EventsCollection, id, mapped)
  }
docs: // Update an event - do NOT update readings
  // UnexpectedError - problem updating in database
  // NotFound - no event with the ID was found