Anticipate relay ID collision

central_backend/src/server/web_api/relays_controller.rs

@@ -39,6 +39,15 @@ pub async fn create(actor: WebEnergyActor, req: web::Json<CreateDeviceRelayReque
         return Ok(HttpResponse::BadRequest().json("Too many relays for the target device!"));
     }
 
+    if actor
+        .send(energy_actor::GetSingleRelay(req.relay.id))
+        .await?
+        .is_some()
+    {
+        log::error!("Invalid relay create query: A relay with the same ID already exists!");
+        return Ok(HttpResponse::BadRequest().json("A relay with the same ID already exists!"));
+    }
+
     // Create the device
     actor
         .send(energy_actor::CreateDeviceRelay(