[Feature]: PRE and POST scripts

[lars18th]

Is your proposal related to a problem?

My problem is related to execute some scripts at the start of the vDSM and when closing.

Describe the solution you'd like.

The idea is to execute some empty scripts inside the container, and we can mount them from a file in the host when running the container. Then we can execute something at the starting point, or closing, etc.
Examples:

/scripts/powerup.sh   (or pre-start.sh)
/scripts/start-run.sh (or post-start.sh)
/scripts/stop-run.sh  (or pre-stop.sh)
/scripts/poweroff.sh  (or post-stop.sh)

Describe alternatives you've considered.

The alternative is to use the docker compose solution. However, in this case we don't have a fine-grane of the scripts executed inside the container to star/stop the qemu virtual machine.

Additional context

If you know about any other similar solution, then please comment.