How do I validate Org.nr (Brønnøysund) + VIES at Magento B2B checkout?

Two B2B identifiers for Norwegian Magento stores, two different validators:

• Org.nr (Organisasjonsnummer), 9-digit Norwegian company ID. Issued + maintained by Brønnøysund Register Centre (Brønnøysundregistrene). Free public API returns company name, address, NACE industry code, MVA-registration status, bankruptcy status. Validate at registration; reject closed / dissolved companies.
• VIES VAT, format NO + 9-digit Org.nr + MVA (e.g. NO123456789MVA). Validated via the EU VIES service. Required for cross-border zero-rated B2B sales to EU customers.

For Magento B2B we:

1. Add Org.nr + VAT-number fields to the customer entity (or B2B company on Adobe Commerce).
2. Validate Org.nr against Brønnøysund API on registration, auto-fills company name + address.
3. Validate the VAT-number against VIES for EU cross-border B2B sales.
4. Apply correct MVA: 25% standard for NO B2C + NO→NO B2B; 0% with reverse-charge for NO→EU B2B with valid VIES VAT.
5. Cache validations 30 days, re-validate on any address change.