https://invoicespec.com/ weekly 1 https://invoicespec.com/xrechnung-api weekly 0.8 https://invoicespec.com/zugferd-api weekly 0.8 https://invoicespec.com/pricing weekly 0.8 https://invoicespec.com/docs weekly 0.8 https://invoicespec.com/docs/getting-started weekly 0.8 https://invoicespec.com/docs/api-reference weekly 0.8 https://invoicespec.com/docs/invoice-json-schema weekly 0.8 https://invoicespec.com/docs/errors weekly 0.8 https://invoicespec.com/docs/glossary weekly 0.8