I'm sending emails using: https://github.com/sendgrid/sendgrid-nodejs/tree/master/packages/mail
I have not been able to find out HOW I can add the <a href="[Unsubscribe]">Unsubscribe</a>
equivalent. This is documented in here: https://sendgrid.com/docs/Classroom/Basics/Marketing_Campaigns/unsubscribe_groups.html#-Using-a-Custom-Unsubscribe-Link
On the website, you just use a shortcode [Unsubscribe], this does not work when sending emails via the sendgrid/mail package.