fix(inbound-api): resolve InboundAPI-014..017 — return-value validation, reflection-gateway hardening, deadline-bound routed calls, RouteHelper test coverage

src/ScadaLink.InboundAPI/IInstanceRouter.cs

@@ -0,0 +1,22 @@
+using ScadaLink.Commons.Messages.InboundApi;
+
+namespace ScadaLink.InboundAPI;
+
+/// <summary>
+/// Seam over the cross-site routing transport used by <see cref="RouteHelper"/>.
+/// The production implementation (<see cref="CommunicationServiceInstanceRouter"/>)
+/// delegates to <c>ScadaLink.Communication.CommunicationService</c>; the interface
+/// exists so <see cref="RouteHelper"/>/<see cref="RouteTarget"/> can be unit tested
+/// without a live actor system (InboundAPI-017).
+/// </summary>
+public interface IInstanceRouter
+{
+    Task<RouteToCallResponse> RouteToCallAsync(
+        string siteId, RouteToCallRequest request, CancellationToken cancellationToken);
+
+    Task<RouteToGetAttributesResponse> RouteToGetAttributesAsync(
+        string siteId, RouteToGetAttributesRequest request, CancellationToken cancellationToken);
+
+    Task<RouteToSetAttributesResponse> RouteToSetAttributesAsync(
+        string siteId, RouteToSetAttributesRequest request, CancellationToken cancellationToken);
+}