Added tests which guard the JSON of providers, the runtime, and services before source generation

app/Tests/Serialization/JsonGoldenRequest.cs

@@ -0,0 +1,15 @@
+using System.Text.Json;
+
+namespace AIStudio.Tests.Serialization;
+
+/// <summary>
+/// A request in the fixtures, together with how AI Studio builds it and the options it writes it with.
+/// </summary>
+/// <param name="FileName">The name of the file in the folder Fixtures next to the tests, which holds the request as it got sent before.</param>
+/// <param name="Create">Builds the request the way AI Studio does.</param>
+/// <param name="Options">The options AI Studio writes the request with.</param>
+public sealed record JsonGoldenRequest(string FileName, Func<object> Create, JsonSerializerOptions Options)
+{
+    /// <inheritdoc />
+    public override string ToString() => this.FileName;
+}