feat(wireguard): add debug logs for IPv6 detection

- To debug issue #998
- Enable with `LOG_LEVEL=debug`

internal/wireguard/route_test.go

@@ -53,7 +53,7 @@ func Test_Wireguard_addRoute(t *testing.T) {
 				Table:     firewallMark,
 			},
 			routeAddErr: errDummy,
-			err:         errors.New("cannot add route {Ifindex: 88 Dst: 1.2.3.4/32 Src: <nil> Gw: <nil> Flags: [] Table: 51820 Realm: 0}: dummy"), //nolint:lll
+			err:         errors.New("cannot add route for link a_bridge, destination 1.2.3.4/32 and table 51820: dummy"), //nolint:lll
 		},
 	}