uuid method
Generates a random UUID.
Implementation
String uuid() {
final bytes = List.generate(16, (_) => _random.nextInt(256));
bytes[6] = (bytes[6] & 0x0f) | 0x40;
bytes[8] = (bytes[8] & 0x3f) | 0x80;
final hex = bytes.map((b) => b.toRadixString(16).padLeft(2, '0')).join();
return '${hex.substring(0, 8)}-${hex.substring(8, 12)}-'
'${hex.substring(12, 16)}-${hex.substring(16, 20)}-${hex.substring(20)}';
}