add upgrade note

Author: valentijnscholten

docs/content/en/open_source/upgrading/2.55.md

@@ -0,0 +1,13 @@
+---
+title: 'Upgrading to DefectDojo Version 2.55.x'
+toc_hide: true
+weight: -20260101
+description: Authorization related optimizations
+---
+
+## Authorization related optimizations
+
+The queries related to authorizations have been optmized. For example retrieving the list of authorized findings for the logged in user.
+Some of these are now also cached during that duration of a request. This should have no functional effects and only results in better performance.
+
+Check the [Release Notes](https://github.com/DefectDojo/django-DefectDojo/releases/tag/2.55.0) for the contents of the release.