docs(database): add section on pg extensions setup

docs/src/deployment/configuration.md

@@ -121,6 +121,36 @@ spring:
     validate-on-migrate: true
 ```
 
+### PostgreSQL extensions
+
+IDP-Core depends on PostgreSQL extensions. They must be installed in the target database before running schema migrations that rely on them.
+
+#### For local development (Docker Compose)
+
+Use the provided initialization script in your `docker-compose.yml`:
+
+```yaml title="docker-compose.yml"
+services:
+  postgres:
+    image: postgres:15
+    volumes:
+      - ./scripts/init-extensions.sql:/docker-entrypoint-initdb.d/01-init-extensions.sql
+```
+
+The script runs automatically on container initialization via the `docker-entrypoint-initdb.d` directory.
+
+#### For production
+
+There are several options depending on your context:
+
+- Provision extensions directly via your Infrastructure as Code (for example Terraform resources)
+- Enable extensions in your cloud provider's database management dashboard
+- Apply the provided initialization script (`/scripts/init-extensions.sql`) using `psql` from your deployment host
+
+Key note:
+
+Installing extensions requires superuser privileges or a role with `CREATE` extension privileges. If your application user lacks these, handle installation as a separate DBA step during provisioning.
+
 ---
 
 ## Application Settings