egid, dta-test file permission

docker-compose.yaml

 version: '2'
-services:
 services:
   mariadb-dtt:
     container_name: moodledb-dtt
@@ -33,7 +32,7 @@ services:
       - mariadb-dtt
   backend:
     container_name: backend
-    image: cota-backend:latest
+    image: hftstuttgart/cota-backend:latest
     user: "${UID}:${GID}"
     volumes: 
       - /var/run/docker.sock:/var/run/docker.sock