Docker containers write files as superuser

By default, docker containers run as root.

Problem: the open and predict commands may write files in the host filesystem. These files are owned by root.

Idealy the image should run as non-privileged user, with the -u/--user option. However, the typical -u $(id -u $USER):$(id -g $USER) option makes Julia virtual environments unreachable within the container, which breaks LarvaTagger.jl.

Alternatively file ownership could be fixed by LarvaTagger.jl.