Merge pull request #4040 from mapfish/renovate/master-postgres-18.x

Update postgres Docker tag to v18 (master)

Author: sbrunner

docker-compose-cluster.yaml

@@ -1,6 +1,6 @@
 services:
   db:
-    image: postgres:15.17
+    image: postgres:18.3
     environment:
       POSTGRES_DB: print
       POSTGRES_USER: print