PostgreSQL upgrade to v18. Closes intelowlproject#3272 (intelowlproject#3292)

* feat: upgrade PostgreSQL to v18 for major release v7.0.0

* Upgrade Postgres to 18-alpine and fix volume mount. Closes intelowlproject#3272 (intelowlproject#3275)

* Upgrade Postgres to 17-alpine and fix volume mount (intelowlproject#3272)

* Upgrade Postgres to 18-alpine as requested

Author: NikhilRaikwar

docker/env_file_postgres_template

@@ -1,3 +1,4 @@
 POSTGRES_PASSWORD=password
 POSTGRES_USER=user
-POSTGRES_DB=intel_owl_db
+POSTGRES_DB=intel_owl_db
+PGDATA=/var/lib/postgresql/pgdata

docker/postgres.override.yml

@@ -1,10 +1,10 @@
 services:
 
   postgres:
-    image: library/postgres:16-alpine
+    image: library/postgres:18-alpine
     container_name: intelowl_postgres
     volumes:
-      - postgres_data:/var/lib/postgresql/data/
+      - postgres_data_v18:/var/lib/postgresql
     env_file:
       - ./env_file_postgres
     healthcheck:
@@ -25,3 +25,6 @@ services:
     depends_on:
       postgres:
         condition: service_healthy
+
+volumes:
+  postgres_data_v18: