test: add backend security regression test foundation

JobTrackerApi.Tests/OwnershipGuardTests.cs

@@ -0,0 +1,22 @@
+using System.Reflection;
+using JobTrackerApi.Controllers;
+using Xunit;
+
+namespace JobTrackerApi.Tests;
+
+public sealed class OwnershipGuardTests
+{
+    [Fact]
+    public void Attachments_controller_has_owned_attachment_lookup_helper()
+    {
+        var method = typeof(AttachmentsController).GetMethod("FindOwnedAttachmentAsync", BindingFlags.NonPublic | BindingFlags.Instance);
+        Assert.NotNull(method);
+    }
+
+    [Fact]
+    public void Correspondence_controller_has_owned_message_lookup_helper()
+    {
+        var method = typeof(CorrespondenceController).GetMethod("FindOwnedMessageAsync", BindingFlags.NonPublic | BindingFlags.Instance);
+        Assert.NotNull(method);
+    }
+}