Fix: Pass actual user ID instead of empty GUID to ExecuteAndWaitForEventAsync in tenant user isolation tests.

Author: aalmada

tests/BookStore.AppHost.Tests/TenantUserIsolationTests.cs

@@ -98,7 +98,7 @@ public async Task AddToFavorites_InSpecificTenant_ShouldUpdateFavorites()
         // Act
         // Act
         // AddBookToFavoritesAsync ?
-        _ = await TestHelpers.ExecuteAndWaitForEventAsync(Guid.Empty, "UserUpdated",
+        _ = await TestHelpers.ExecuteAndWaitForEventAsync(userClient.UserId, "UserUpdated",
             async () => await userBooksClient.AddBookToFavoritesAsync(book.Id),
             TestConstants.DefaultEventTimeout);