generateVerifyEmailToken = async (user) => {
  const expires = moment().add(config.jwt.verifyEmailExpirationMinutes, 'minutes');
  const verifyEmailToken = generateToken(user.id, expires, tokenTypes.VERIFY_EMAIL);
  await saveToken(verifyEmailToken, user.id, expires, tokenTypes.VERIFY_EMAIL);
  return verifyEmailToken;
}
Generate verify email token
@param {User} user
@returns {Promise<string>}