Update for flexible container configuration

- Allow custom image name override via IMAGE env var
- Enable container name configuration through NAME env var
- Set container user/group via RUN_USER and RUN_GROUP

docker-compose.yml

@@ -8,7 +8,9 @@ networks:
 
 services:
   prometheus:
-    image: prom/prometheus:${VERSION:?}
+    image: ${IMAGE:-prom/prometheus}:${VERSION:?}
+    container_name: ${NAME:-prometheus}
+    user: ${RUN_USER:-1000}:${RUN_GROUP:-1000}
     volumes:
       - config:/etc/prometheus
       - data:/prometheus