docs: postgres 18 documentation (#2046)

Signed-off-by: Ludovic Ortega <ludovic.ortega@adminafk.fr>

Author: M0NsTeRRR

compose.postgres.yaml

@@ -23,14 +23,14 @@ services:
     links:
       - postgres
   postgres:
-    image: postgres
+    image: postgres:18
     environment:
       POSTGRES_USER: jellyseerr
       POSTGRES_PASSWORD: jellyseerr
       POSTGRES_DB: jellyseerr
     ports:
       - '5432:5432'
     volumes:
-      - postgres:/var/lib/postgresql/data
+      - postgres:var/lib/postgresql/18/docker
 volumes:
   postgres:

docs/extending-jellyseerr/database-config.mdx

@@ -20,7 +20,8 @@ DB_LOG_QUERIES="false" # (optional) Whether to log the DB queries for debugging.
 ## PostgreSQL Options
 
 :::caution
-When migrating Postgres from version 17 to 18 in Docker, note that the data mount point has changed. Instead of using `/var/lib/postgresql/data`, the correct mount path is now `/var/lib/postgresql`.
+When migrating Postgres from version 17 to 18 in Docker, note that the data mount point has changed. Instead of using `/var/lib/postgresql/data`, the correct mount path is now `/var/lib/postgresql/18/docker`.
+Refer to the [PostgreSQL Docker documentation](https://hub.docker.com/_/postgres/#pgdata) to learn how to migrate or opt out of this change.
 :::
 
 ### TCP Connection