Add option to install Docker rootless mode via parameter

For some catalog items you might not want to have a rootful Docker installed from which you could potentially gain root access to mounted directories as a non-root user. For that reason, Docker also offers the rootless mode.

Setting the docker_rootless parameter will trigger a different set of task than the regular (rootful) Docker installation. Since the rootless version of Docker runs in the user space, rather than as a rootful daemon, the installation needs to happen per user.

Rootless installation steps

• Install necessary packages
• Compile list of active users in workspace (uids > 1000)
• For each active user:
  • Enable lingering of (systemd) user services to have docker enabled even after reboot
  • Configure Docker rootless for user
  • Start Docker rootless service