sendVerificationEmail = async (to, token) => {
  const subject = 'Email Verification';
  // replace this url with the link to the email verification page of your front-end app
  const verificationEmailUrl = `http://link-to-app/verify-email?token=${token}`;
  const text = `Dear user,
To verify your email, click on this link: ${verificationEmailUrl}
If you did not create an account, then ignore this email.`;
  await sendEmail(to, subject, text);
}
Send verification email
@param {string} to
@param {string} token
@returns {Promise}