https://iabtechlab.com/wp-content/uploads/2019/03/IAB-OpenRTB-Ads.txt-Public-Spec-1.0.2.pdf
- validate domains format
- validate relationship
- validate record format (domain/pub_id/relationship)
- validate variable type (contact/subdomain)
- follow and merge subdomains ads.txt
- filter out comments
- flag duplicated lines
todo:
- domain name misspelling checking ?
- certification id verification ?