feat(notification-outbox): add Notification entity

tests/ScadaLink.Commons.Tests/Entities/NotificationEntityTests.cs

@@ -0,0 +1,33 @@
+using ScadaLink.Commons.Entities.Notifications;
+using ScadaLink.Commons.Types.Enums;
+
+namespace ScadaLink.Commons.Tests.Entities;
+
+/// <summary>
+/// Verifies the <see cref="Notification"/> outbox entity's constructor defaults
+/// and null-argument guards on required reference-type parameters.
+/// </summary>
+public class NotificationEntityTests
+{
+    [Fact]
+    public void Constructor_SetsDefaults()
+    {
+        var n = new Notification("id-1", NotificationType.Email, "ops-team", "subj", "body", "SiteA");
+        Assert.Equal(NotificationStatus.Pending, n.Status);
+        Assert.Equal(0, n.RetryCount);
+        Assert.Equal("id-1", n.NotificationId);
+        Assert.Equal(NotificationType.Email, n.Type);
+        Assert.Equal("ops-team", n.ListName);
+        Assert.Equal("SiteA", n.SourceSiteId);
+    }
+
+    [Fact]
+    public void Constructor_NullListName_Throws()
+        => Assert.Throws<ArgumentNullException>(
+            () => new Notification("id", NotificationType.Email, null!, "s", "b", "SiteA"));
+
+    [Fact]
+    public void Constructor_NullNotificationId_Throws()
+        => Assert.Throws<ArgumentNullException>(
+            () => new Notification(null!, NotificationType.Email, "list", "s", "b", "SiteA"));
+}