Add defang config command example for POSTGRES_SSL configuration

Co-authored-by: lionello <[email protected]>

Author: Copilot

samples/nextjs-postgres/README.md

@@ -27,7 +27,11 @@ A password that will be used to connect to the Postgres database.
 
 ## Database Configuration
 
-This sample is configured to work with standard PostgreSQL containers that don't have SSL enabled. The production configuration uses `POSTGRES_SSL: false` to ensure compatibility with the default `postgres:16` Docker image. If you're using a managed PostgreSQL service with SSL support, you can set `POSTGRES_SSL: true` in your compose.yaml file.
+This sample is configured to work with standard PostgreSQL containers that don't have SSL enabled. The production configuration uses `POSTGRES_SSL: false` to ensure compatibility with the default `postgres:16` Docker image. If you're using a managed PostgreSQL service with SSL support, you can set `POSTGRES_SSL: true` in your compose.yaml file, or override it using `defang config`:
+
+```bash
+defang config set POSTGRES_SSL=true
+```
 
 
 ## Deploying