Refactor lmn_vpn role

- Separate `lmn_vpn` from `lmn_teacherlaptop`.
- Implement a check for the availability of the wireguard-server during the wg-config rollout.
- Enhance variable support with a standardized naming schema:
  - VPN selection via `vpn` variable (`none`, `wg`).
  - Wireguard configuration (endpoint, allowed IPs, ip_cdr, dns, searchpath).
- Run wg-config role in separate play with serial 1 to avoid conflicts, when the role attempts
  to determine the next free Wireguard IP on the server when role try to Add a check to verify if the radius certificate is revoked.
- Ensure required packages and services are only installed and configured if the `vpn` variable is set.
- Provide documentation for `lmn_vpn` module.

roles/lmn_vpn/files/mountserver

@@ -0,0 +1,26 @@
+#!/usr/bin/bash
+set -eu
+
+exit_script() {
+    echo "unmounting media - terminated by trap!" >> "/tmp/${SUDO_UID}-exit-mount.log"
+    findmnt "/lmn/media/${SUDO_USER}/share" && umount "/lmn/media/${SUDO_USER}/share"
+    findmnt "/srv/samba/schools/default-school" && umount "/srv/samba/schools/default-school"
+    trap - SIGHUP SIGINT SIGTERM # clear the trap
+    kill -- -$$ # Sends SIGTERM to child/sub processes
+}
+
+findmnt /srv/samba/schools/default-school > /dev/null && exit 0
+
+umask 0002
+mkdir -p /srv/samba/schools/default-school
+chmod 777  /srv/samba/schools/default-school
+mkdir -p "/lmn/media/${SUDO_USER}/share"
+
+mount -t cifs //server/default-school/ /srv/samba/schools/default-school \
+      -o "sec=krb5i,cruid=${SUDO_UID},user=${SUDO_USER},uid=${SUDO_UID},gid=${SUDO_GID},file_mode=0700,dir_mode=0700,mfsymlinks,nobrl,actimeo=600,cache=loose,echo_interval=10"
+mount --bind /srv/samba/schools/default-school/share "/lmn/media/${SUDO_USER}/share"
+
+echo "Einbindung erfolgreich!"
+echo "Dieses Fenster bitte nicht schließen!"
+trap exit_script SIGHUP SIGINT SIGTERM
+sleep infinity