return tagDao.findByName(tagName)
.map(tag -> giftCertificateDao.findByTag(tag)
.stream()
.map(giftCertificate -> modelMapper.map(giftCertificate, GiftCertificateDto.class))
.collect(Collectors.toSet()))
.orElseThrow(() -> new EntityNotFoundException(MESSAGE_ENTITY_NOT_FOUND_EXCEPTION));