docs: static String toFormattedString(final String iban) {
          final StringBuilder ibanBuffer = new StringBuilder(iban);
          final int length = ibanBuffer.length();
  
          for (int i = 0; i < length / 4; i++) {
              ibanBuffer.insert((i + 1) * 4 + i, ' ');
          }
  
          return ibanBuffer.toString().trim();
      }