As an AuthCode.
Source
AuthCode asAuthCode() { return new AuthCode() ..hasBeenExchanged = accessToken != null ..code = code ..resourceOwnerIdentifier = resourceOwner.id ..issueDate = issueDate ..requestedScopes = scope?.split(" ")?.map((s) => new AuthScope(s))?.toList() ..expirationDate = expirationDate ..clientID = client.id; }