Fix immediate unsubscribe of participants
From &3758 (comment 1938939280)
I realised the following when it comes to how a user wants to unsubscribe from a ticket:
- Currently, Gitlab sends an HTTP GET request to a specific endpoint when the user wants to unsubscribe
- The standard is to implement the Unsubscribe functionality using the List-Unsubscribe email header field, instead of an API endpoint as currently implemented (see RFC8058)
This causes some of our clients to get unsubscribed from a ticket automatically when the SMTP Application Firewall scans the email, hereby I mean at reception of the email. By definition, I'd therefore consider this a bug.
This abstract can resume the issue similarly:
This document describes a method for signaling a one-click function for the List-Unsubscribe email header field. The need for this arises out of the actuality that mail software sometimes fetches URLs in mail header fields, and thereby accidentally triggers unsubscriptions in the case of the List-Unsubscribe header field.
Edited by Marc Saleiko