ECSatize AlertsSystem (#5559)

Content.Server/Alert/ServerAlertsSystem.cs

@@ -0,0 +1,7 @@
+using Content.Shared.Alert;
+
+namespace Content.Server.Alert;
+
+// The only reason this exists is because the DI system requires the shared AlertsSystem
+// to be abstract.
+internal class ServerAlertsSystem : AlertsSystem { }