PROTOTYPE: Auth separation

Src/Support/Google.Apis.Auth/ExistingDependencies/ReplacementSerializer.cs

@@ -0,0 +1,19 @@
+using Google.Apis.Auth.OAuth2;
+using System;
+using System.IO;
+using System.Threading;
+using System.Threading.Tasks;
+
+namespace Google.Apis.Auth.ExistingDependencies;
+
+// The replacement for NewtonsoftJsonSerializer
+internal class ReplacementSerializer
+{
+    internal static string Serialize<T>(T value) => default;
+
+    internal static T Deserialize<T>(string json) => default;
+
+    public static Task<T> DeserializeAsync<T>(Stream stream, CancellationToken cancellationToken) => default;
+
+    public static T Deserialize<T>(Stream stream) => default;
+}

Src/Support/Google.Apis.Auth/JsonWebSignature.cs

@@ -51,7 +51,7 @@ public static Task<Payload> VerifySignedTokenAsync(
         /// <exception cref="InvalidJwtException">If the token is invalid or expired.</exception>
         /// <typeparam name="TPayload">The type of the payload to return, so user code can validate
         /// additional claims. Should extend <see cref="Payload"/>. Payload information will be deserialized
-        /// using <see cref="NewtonsoftJsonSerializer.Instance"/>.</typeparam>
+        /// using the default serializer.</typeparam>
         public async static Task<TPayload> VerifySignedTokenAsync<TPayload>(
             string signedJwt, SignedTokenVerificationOptions options = null, CancellationToken cancellationToken = default)
             where TPayload : Payload