randomUsername static method
Generate a random username.
Implementation
static String randomUsername({int minLength = 6, int maxLength = 12}) {
  const letters = 'abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
  const numbers = '0123456789';
  const specialChars = '_-.';
  const allChars = letters + numbers + specialChars;
  // Random length between minLength and maxLength
  final length = _random.nextInt(maxLength - minLength + 1) + minLength;
  // Ensure the username starts with a letter
  final firstChar = letters[_random.nextInt(letters.length)];
  // Generate the rest of the username
  final restChars = List.generate(length - 1, (_) {
    return allChars[_random.nextInt(allChars.length)];
  }).join();
  return firstChar + restChars;
}