code: public static final AuthToken createAuthToken(String principal, Set<String> roles, int expiresInMillis) {
          AuthToken token = new AuthToken();
          token.setIssuedOn(new Date());
          token.setExpiresOn(new Date(System.currentTimeMillis() + expiresInMillis));
          token.setPrincipal(principal);
          token.setRoles(roles);
          signAuthToken(token);
          return token;
      }
docs: Creates an auth token.
  @param principal the auth principal
  @param roles the auth roles
  @param expiresInMillis the number of millis to expiry
  @return the auth token