code: @CommandArgument
    public void adduser(
        @OptionArgument("username") String username,
        @OptionArgument("password") String password,
        @OptionArgument("roles") String roles) {
  
      if (users.containsKey(username)) {
        System.err.println(String.format("User '%s' already exists", username));
      } else {
  
        User user = new User(username);
        user.salt = passwd.generateSalt();
        user.hash = passwd.getEncryptedPassword(password, user.salt);
        user.roles.addAll(Arrays.asList(roles.split(",")));
        users.put(username, user);
  
      }
    }
docs: Adds a new user.
  @param username The username.
  @param password The password.
  @param roles A comma-separated list of roles that the new user will have.