Persist ip tables and ip route after reboot:

1. Persist IP tables:

   sudo netfilter-persistent save

2. Create IP route script:

   cd /usr/local/sbin
   sudo touch wireguard.sh
   sudo chmod u+x wireguard.sh
   sudo vim wireguard.sh

3. Copy paste below script to vim or nano:

   #!/bin/bash
   
   # Define the route details
   ROUTE="10.8.0.0/24"
   GATEWAY="172.18.0.2"
   
   # Check if the route already exists
   if ip route show $ROUTE | grep -q "via $GATEWAY"; then
       echo "Route $ROUTE via $GATEWAY already exists."
       exit 0
   else
       # Attempt to add the route
       if ip route add $ROUTE via $GATEWAY; then
           echo "Route $ROUTE via $GATEWAY added successfully."
           exit 0
       else
           echo "Wireguard container is not running yet. Restarting in 5 seconds."
           exit 1
       fi
   fi

4. Create systemctl service:

   sudo vim /etc/systemd/system/wireguard.service

5. Copy paste below service file:

   [Unit]
   Description=Expose wireguard peer to host
   After=network.target
   
   [Service]
   Type=oneshot
   ExecStart=/usr/local/sbin/wireguard.sh
   Restart=on-failure
   RestartSec=5
   RemainAfterExit=yes
   
   [Install]
   WantedBy=multi-user.target

6. Run service and make sure it is running:

   sudo systemctl daemon-reload
   sudo systemctl enable wireguard
   sudo systemctl start wireguard
   sudo systemctl status wireguard

7. All done, now you can reboot without issue.

Topology of this archicture to make it more clear: