Updated the backend docker compose file and also added dockercompose for mongo and mongo express

backend-server/Dockerfile

@@ -14,6 +14,12 @@ RUN npm install --save-dev @types/cors
 
 COPY .  .
 
+USER root
+
+RUN chown -R node:node /app
+
+USER node
+
 EXPOSE 3000
 
 CMD ["npm","start"]