private (string stateId, ActionToken clientToken) UnpackState(string state)
{
var startAt = state.LastIndexOf(TokenSeparator);
var stateId = new string(state.AsSpan(0, startAt));
var clientTokenRaw = state.AsSpan(startAt + 1);
if (!ActionToken.TryParse(clientTokenRaw, out var clientToken))
{
return(default);