fix docker-compose.yml to add default values

Author: NONstop5

docker-compose.yml

@@ -13,11 +13,11 @@ services:
     image: postgres:latest
     restart: unless-stopped
     environment:
-        POSTGRES_DB: ${DATABASE_NAME}
-        POSTGRES_USER: ${DATABASE_USERNAME}
-        POSTGRES_PASSWORD: ${DATABASE_PASSWORD}
+        POSTGRES_DB: ${DATABASE_NAME:-postgres}
+        POSTGRES_USER: ${DATABASE_USERNAME:-postgres}
+        POSTGRES_PASSWORD: ${DATABASE_PASSWORD:-password}
     ports:
-        - "${DATABASE_PORT}:5432"
+        - "${DATABASE_PORT:-5432}:5432"
     volumes:
       - pgdata:/var/lib/postgresql/data
     healthcheck: