In order to have Error Tracking to work correctly, we need to report either `error.kind` or `error.stack` (see [docs](https://docs.datadoghq.com/logs/error_tracking/backend/?tab=serilog#attributes-for-error-tracking)). Today the library only reports `error.stack` for crashes ([permalink](https://github.com/Nebo15/logger_json/blob/584a6243b66dbd074c1e87a177a278070005ab12/lib/logger_json/formatters/datadog.ex#L101)).