when working with docker, we need to be able to tell the db.py DB class, where the postgresql DB resides (a different host, a different docker container, unix named pipe , etc.)
[x] make the DSN configurable, assume safe default values
[ ] document it in the README.md / installation manual
when working with docker, we need to be able to tell the db.py DB class, where the postgresql DB resides (a different host, a different docker container, unix named pipe , etc.)