Made the JSON types of the providers settable instead of init-only

app/MindWork AI Studio/Tools/Source.cs

@@ -5,4 +5,15 @@ namespace AIStudio.Tools;
 /// </summary>
 /// <param name="Title">The title of the source.</param>
 /// <param name="URL">The URL of the source.</param>
-public record Source(string Title, string URL, SourceOrigin Origin) : ISource;
+public record Source(string Title, string URL, SourceOrigin Origin) : ISource
+{
+    //
+    // The properties of the parameters, declared again to be settable. A derived record which passes a value of
+    // its own to one of them, as the search results of Perplexity do with the origin, would otherwise lose it:
+    // the source generation of System.Text.Json sets every init-only property while it creates the object, also
+    // one missing in the JSON. Keep them in the order of the parameters, which is the order they get stored in:
+    //
+    public string Title { get; set; } = Title;
+    public string URL { get; set; } = URL;
+    public SourceOrigin Origin { get; set; } = Origin;
+}