Generated the JSON contracts of the stored data at compile time (#1148)

app/Tests/Serialization/JsonTestRoot.cs

@@ -0,0 +1,14 @@
+using System.Text.Json;
+
+namespace AIStudio.Tests.Serialization;
+
+/// <summary>
+/// A type which AI Studio reads or writes as JSON on its own, together with the options it uses for that.
+/// </summary>
+/// <param name="Type">The type which gets serialized. Whatever it holds gets checked along with it.</param>
+/// <param name="Options">The options AI Studio passes to System.Text.Json for this type.</param>
+public sealed record JsonTestRoot(Type Type, JsonSerializerOptions Options)
+{
+    /// <inheritdoc />
+    public override string ToString() => JsonContractDescription.TypeName(this.Type);
+}