Switch to official postfixadmin image
The hardware/postfixadmin image we are using as base has its latest tagged release 7 months ago. Since then they are only pushing to the :latest tag. This obviously means that we are behind on bug fixes and security fixes.
In particular, this bug is currently fixed by copying postfixadmin-cli.php in our own Dockerfile.
The disadvantage is that the official docker image has almost 400 mb, now it is only 44 mb (unless we can use the alpine-fpm image somehow).