docs: update oncall stack

Author: raisedadead

docker/swarm/stacks/oncall/README.md

@@ -115,19 +115,25 @@ Trigger an on-demand Gantry update from a GitHub Actions workflow:
 
 ## Testing Webhook
 
-Manual curl examples for verifying the webhook service:
+Run from the manager node (`ssh freecodecamp@ops-vm-backoffice`):
 
 ```bash
-# Valid request (with secret header)
+# Trigger update for a specific service
 curl -X POST http://localhost:9889/hooks/run-gantry \
   -H "Content-Type: application/json" \
-  -H "X-Webhook-Secret: YOUR_SECRET_HERE" \
-  -d '{"GANTRY_SERVICES_FILTERS":"name=mystack_myservice"}'
+  -H "X-Webhook-Secret: $WEBHOOK_SECRET" \
+  -d '{"GANTRY_SERVICES_FILTERS":"name=<stack>_<service>"}'
 
-# Invalid request (without secret — should be rejected)
+# Trigger update for all autoupdate-labeled services (no filter)
 curl -X POST http://localhost:9889/hooks/run-gantry \
   -H "Content-Type: application/json" \
-  -d '{"GANTRY_SERVICES_FILTERS":"name=mystack_myservice"}'
+  -H "X-Webhook-Secret: $WEBHOOK_SECRET" \
+  -d '{}'
+
+# Invalid request (no secret — should return "Hook rules were not satisfied")
+curl -X POST http://localhost:9889/hooks/run-gantry \
+  -H "Content-Type: application/json" \
+  -d '{}'
 
 # Check webhook logs
 docker service logs oncall_svc-webhook