db user name and password are now configured by environment variables

docker-compose.yml

@@ -16,6 +16,9 @@ services:
       dockerfile: PHP.Dockerfile
     volumes:
       - ./app:/app
+    environment:
+      DB_USER_NAME: 'grisu'
+      DB_PASS: 'secret'
   mysql:
     image: mariadb:latest
     environment: