Update a trunk description when it is migrated

A description could be outdated when migrating to a router in a new site. (E.g. moving from ATH1 to ATH2) Hasn't happened yet AFAIK, but would like to prevent this from happening

gso/workflows/iptrunk/migrate_iptrunk.py

@@ -762,6 +762,15 @@ def update_subscription_model(
             IptrunkInterfaceBlock.new(subscription_id=uuid4(), **member),
         )
 
+    # Take the new site names, and update the subscription description
+    side_names = sorted([
+        subscription.iptrunk.iptrunk_sides[0].iptrunk_side_node.router_site.site_name,
+        subscription.iptrunk.iptrunk_sides[1].iptrunk_side_node.router_site.site_name,
+    ])
+    subscription.description = (
+        f"IP trunk {side_names[0]} {side_names[1]}, geant_s_sid:{subscription.iptrunk.geant_s_sid}"
+    )
+
     return {"subscription": subscription}