sdk: LoginWithCustomAsync + regenerated auth models

Exceptions/RudderAuthException.cs

@@ -0,0 +1,15 @@
+namespace RudderSdk.Core;
+
+/// <summary>
+/// The server rejected the request as unauthenticated (HTTP 401). The SDK
+/// attempts a token refresh before surfacing this; seeing it means the session
+/// is over and the player must sign in again.
+/// </summary>
+public sealed class RudderAuthException : RudderApiException
+{
+    /// <summary>Creates the exception.</summary>
+    public RudderAuthException(int statusCode, string? code, string message, string? requestId = null)
+        : base(statusCode, code, message, requestId)
+    {
+    }
+}