- 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.
