- Added PeppolValidator class to validate PEPPOL BIS 3.0 invoices, including checks for endpoint IDs, document type IDs, process IDs, party identification, and business rules.
- Implemented validation for GLN check digits, document types, and transport protocols specific to PEPPOL.
- Added XRechnungValidator class to validate XRechnung 3.0 invoices, focusing on German-specific requirements such as Leitweg-ID, payment details, seller contact, and tax registration.
- Included validation for IBAN and BIC formats, ensuring compliance with SEPA regulations.
- Established methods for checking B2G invoice indicators and validating mandatory fields for both validators.
- Added validation types for EN16931 compliance in `validation.types.ts`, including interfaces for `ValidationResult`, `ValidationOptions`, and `ValidationReport`.
- Introduced `VATCategoriesValidator` in `vat-categories.validator.ts` to validate VAT categories according to EN16931 rules, including detailed checks for standard, zero-rated, exempt, reverse charge, intra-community, export, and out-of-scope services.
- Enhanced `IEInvoiceMetadata` interface in `en16931-metadata.ts` to include additional fields required for full standards compliance, such as delivery information, payment information, allowances, and charges.
- Implemented helper methods for VAT calculations and validation logic to ensure accurate compliance with EN16931 standards.
