fix(doc): Breaking Change for HELM deployments with PostgreSQL (#10524)

Author: kiblik

docs/content/en/getting_started/upgrading/2.36.md

@@ -2,6 +2,15 @@
 title: 'Upgrading to DefectDojo Version 2.36.x'
 toc_hide: true
 weight: -20240603
-description: No special instructions.
+description: Breaking Change for HELM deployments with PostgreSQL
 ---
-There are no special instructions for upgrading to 2.36.x. Check the [Release Notes](https://github.com/DefectDojo/django-DefectDojo/releases/tag/2.36.0) for the contents of the release.
+
+Previous HELM deployments (HELM chart `<=1.6.136`, DefectDojo `<=2.35.4`) used a pinned version of PostgreSQL in versions `11.x`. These are incompatible with Django in version `4.2` (used from DefectDojo version `3.36.0`; HELM chart `1.6.137`). Because of this, it is necessary to upgrade PostgreSQL to version `12.x` or higher. DefectDojo in version `3.36.1` (HELM chart `1.6.138`) uses this new version of PostgreSQL.
+
+Unfortunately, an upgrade of PostgreSQL is not enough because PostgreSQL does not support automatic migration of data structures in the filesystem. Because of this, migration is needed. There are different ways (many of them similar to migration between different database backends (e.g. from MySQL to PostgreSQL)). Please find inspiration and the best fitting way for you in:
+
+- https://github.com/DefectDojo/django-DefectDojo/discussions/9480
+- https://owasp.slack.com/archives/C2P5BA8MN/p1717610931766739?thread_ts=1717587117.831149&cid=C2P5BA8MN
+- https://dev.to/jkostolansky/how-to-upgrade-postgresql-from-11-to-12-2la6
+
+There are no other special instructions for upgrading to 2.36.x. Check the [Release Notes](https://github.com/DefectDojo/django-DefectDojo/releases/tag/2.36.0) for the contents of the release.