curl --request POST \
  --url https://core-proxy-service-w34nvoxnwq-uc.a.run.app/proxy_api/v1/iproyal/users/add_balance \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "user_id": "<string>",
  "data_gb": 123
}
'

{
  "user_id": 12345,
  "data_gb": 123,
  "used_traffic": 123
}