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;
}