Added an introduction and an onboarding chat to the BeyondFacts Lab (#1178)

app/MindWork AI Studio/Assistants/BeyondFactsLab/BflThreadLocation.cs

@@ -1,14 +1,26 @@
 namespace AIStudio.Assistants.BeyondFactsLab;
 
 /// <summary>
-/// Where the BeyondFacts Lab keeps a chat: the step of a preparation it belongs to.
+/// Where the BeyondFacts Lab keeps a chat, e.g., in a step of a preparation.
 /// </summary>
-/// <param name="ProjectId">The ID of the preparation.</param>
-/// <param name="Step">The step.</param>
-public readonly record struct BflThreadLocation(Guid ProjectId, BflStep Step)
+/// <remarks>
+/// Each place holds one chat at most, and the ID of the chat follows from the place, see BflThreadId. Two places of
+/// the same kind with the same values are equal, so a place serves as a key.
+/// </remarks>
+public abstract record BflThreadLocation
 {
     /// <summary>
-    /// Gets the ID of the chat, which follows from its place, see BflThreadId.
+    /// Gets the ID of the chat, which follows from its place.
     /// </summary>
-    public Guid ChatId => BflThreadId.Of(this.ProjectId, this.Step);
+    public abstract Guid ChatId { get; }
+
+    /// <summary>
+    /// Gets a key which no other place has, e.g., for the registry of running assistant sessions and for the log.
+    /// </summary>
+    public abstract string Key { get; }
+
+    /// <summary>
+    /// Gets the name the chat stores, which tells people who look into its file where it belongs.
+    /// </summary>
+    public abstract string ChatName { get; }
 }