HTTP_mirror_pool.md

@@ -9,6 +9,8 @@ See the corresponding [design document](https://tails.boum.org/contribute/design
 
 # Improve UX and lower maintenance cost (2021)
 
+Tracking issue: tails#18262
+
 ## Current problems
 
 Our current mirror pool, and how we use and maintain it, has several major