Missing documentation: how to configure CodiMD container when using recommended docker-hackmd deployment

I just started a CodiMD instance using the [Docker deployment](https://github.com/hackmdio/docker-hackmd) approach recommended [here](https://hackmd.io/c/codimd-documentation/%2Fs%2Fcodimd-docker-deployment) and everything worked _nearly_ out of the box. Great work!

Nevertheless Email authentication does not work for me and I can't find documentation which helps me out:

- When I try to register by mail I just get an error "Invalid email or password."
- How would I see CodiMD error logs?
- Is there a way to configure CodiMD as described [here](https://hackmd.io/c/codimd-documentation/%2Fs%2Fcodimd-configuration) when I use the Docker deploy method?
- I'd like to post this issue in the [docker-hackmd](https://github.com/hackmdio/docker-hackmd) repository but it's read-only. is there another way to ask for support regarding that repository?