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

app/Tests/Serialization/JsonGoldenFile.cs

@@ -0,0 +1,15 @@
+using System.Text.Json;
+
+namespace AIStudio.Tests.Serialization;
+
+/// <summary>
+/// A stored file in the fixtures, together with the type and the options AI Studio reads it with.
+/// </summary>
+/// <param name="FileName">The name of the file in the folder Fixtures next to the tests.</param>
+/// <param name="Type">The type AI Studio reads the file as.</param>
+/// <param name="Options">The options AI Studio reads and writes the file with.</param>
+public sealed record JsonGoldenFile(string FileName, Type Type, JsonSerializerOptions Options)
+{
+    /// <inheritdoc />
+    public override string ToString() => this.FileName;
+}