Add support for Oman TIN

[unho]

• https://www.oecd.org/tax/automatic-exchange/crs-implementation-and-assistance/tax-identification-numbers/Oman-TIN.pdf

  There structure of TIN may differ depending on type of taxes. For the VAT and Excise Tax, the TIN
  consists of 12 alphabetic- numeric characters. However, for entities TIN number is only in numeric
  sequence and currently is up to seven-digit sequence.

  • Either 7 digits, or 12 alphanumeric characters.
    • My suspicion is that the 12 alphanumeric are OM characters then followed by 10 digits.
      • This suspicion is kinda confirmed by searching some of the found examples in the online validation page URL listed below.
    • I also suspect that the 7 digits is called Tax Card Number and the 12 alphanumeric is called VATIN.
      • This suspicion is also kinda confirmed by searching some of the found examples in the online validation page URL listed below.
• https://www.omanobserver.om/article/87104/Main/tax-card-with-unique-number-now-must-for-entities

Online validation:

• Using the VATIN on https://www.taxoman.gov.om/portal/web/taxportal/tax-data-validation

VATIN Examples:

• OM1100006083 from https://www.omantel.om/wcm/connect/7041d8b4-9865-4974-9980-97c13a7589e6/VatCertificate.pdf?MOD=AJPERES&CVID=nzr8s9j&CVID=nzr8s9j&CVID=nzr8s9j
• OM1100018164 from https://www.muzn.om/en/Pages/VAT.aspx
• OM1100011333 from https://mzec.nama.om/SiteAssets/mzec/documents/MZEC%20VAT%20Certificate%202022.pdf
• https://www.g4s.com/en-om

  OM1100002920
  OM1100006999

• https://www.google.com/search?q=site%3A.om+%22VATIN%22
• https://www.google.com/search?q=site%3A.om+%22Tax+Card+Number%22
• https://www.google.com/search?q=site%3A.om+%22tax+card+no%22
• https://www.google.com/search?q=site%3A.om+%22TIN%22
• https://www.google.com/search?q=site%3A.om+%22VAT+registration+number%22