RSS tags feed of private/protected projects leads to login-page

Summary

When trying to add RSS feed of "tags" of a private/protected project the feeds URL is invalid or "feed url needs authorization"

Steps to reproduce

Create a private or protected project and try to get an RSS feed into your feedreader (I tested with Thunderbird)

Example Project

Happens on gitlab.com, I can't link to a project as I can't create a "protected" project, only a private project where only I have access, so not useful here

What is the current bug behavior?

Redirected to login page

What is the expected correct behavior?

get atom feed for Thunderbird to work

Output of checks

This bug happens on GitLab.com