Added a way to read what the AI received from your sources (#1100)

Co-authored-by: Thorsten Sommer <SommerEngineering@users.noreply.github.com>

app/Tests/Chat/ChatThreadAugmentedDataTests.cs

@@ -0,0 +1,51 @@
+using System.Text.Json;
+
+using AIStudio.Chat;
+using AIStudio.Tools;
+
+namespace AIStudio.Tests.Chat;
+
+/// <summary>
+/// Checks that the augmented data of the classic RAG process stays with the request it was made for.
+/// </summary>
+/// <remarks>
+/// The process writes it anew for every message, so a stored copy was never read again, while it
+/// often made up the largest part of a chat file. What the AI read of it is kept with the answer as
+/// its passages.
+/// </remarks>
+[TestFixture]
+public sealed class ChatThreadAugmentedDataTests
+{
+    [Test]
+    public void TheAugmentedDataIsNotSaved()
+    {
+        var thread = new ChatThread { ChatId = Guid.NewGuid(), AugmentedData = "# Retrieval context 1 of 1\nThe mixing console is described here." };
+
+        var json = JsonSerializer.Serialize(thread, WorkspaceBehaviour.JSON_OPTIONS);
+        using var document = JsonDocument.Parse(json);
+
+        Assert.That(document.RootElement.TryGetProperty("augmented_data", out _), Is.False);
+    }
+
+    [Test]
+    public void AChatSavedWithAugmentedDataLoadsWithout()
+    {
+        const string CHAT_WITH_AUGMENTED_DATA = """
+                                                {
+                                                  "chat_id": "2b7c9e1f-4a6d-4c8b-9e3f-1d5a7c9b2e4f",
+                                                  "name": "An older chat",
+                                                  "augmented_data": "# Retrieval context 1 of 1\nThe mixing console is described here.",
+                                                  "blocks": []
+                                                }
+                                                """;
+
+        var loaded = JsonSerializer.Deserialize<ChatThread>(CHAT_WITH_AUGMENTED_DATA, WorkspaceBehaviour.JSON_OPTIONS);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(loaded, Is.Not.Null, "An older chat file must still load.");
+            Assert.That(loaded!.AugmentedData, Is.Empty, "It belonged to a request long over; the next message retrieves anew.");
+            Assert.That(loaded.Name, Is.EqualTo("An older chat"));
+        });
+    }
+}