Added database_url variable to staging deployment configuration in…

Added database_url variable to staging deployment configuration in .gitlab-ci.yml for backend deployment.

.gitlab-ci.yml

@@ -60,6 +60,7 @@ deploy_backend_staging:
   variables:
     app_env: staging
     app_url: https://spin-wheel-backend-staging.kacdn.net
+    database_url: ${DATABASE_URL}
   script:
     - deploy-ecs staging
   only: