Setup Jupyter password during first login

[tomuben]

Background

Currently the Jupyter password is set statically by Ansible, see here.
It could be a problem to have a static password for all VM images. It would be better to create a password dynamically during the first boot of the VM and then show it to the user during login.

For that purpose we could create shell script which is executed by systemd. The script checks if the Jupyter password file (under ~/.jupyter/jupyter_notebook_config.json) exists, and if not, creates a new random password.

We can then use motd to show the password to the user during login.

Acceptance Criteria

1. Remove the static creation of the password via Ansible
2. Create a script which checks if the Jupyter config file already exists (~/.jupyter/jupyter_notebook_config.json) and if not creates a new random password
3. Add a systemd service which runs the script during the first boot (via Ansible)
4. Use Motd to show the Jupyter pasword during login