Log integrations

I'm not sure if I should write here or not. Nice product! I will try to use it in all my environments.
But I'm already curious about logs collecting not only from my apps but also Nginx, for example.
I have Nginx locally installed and also in a docker container. I know, that there is a way to write Docker logs driver, but as I know, it gets only a string from service output, so no key=value for matching, just plain log https://docs.docker.com/engine/extend/plugins_logging/.
There is a hacky way for Nginx to output JSON format, but I'm not sure how to transfer file or stream? To API in a docker container. I guess in this situation an Nginx plugin is needed.

I'm not asking for this, just curious if you have plans to collect logs from not programmable sources.