Session token is missing from signed request headers

The session token is missing from the call to Sign(), which causes authentication to fail when using temporary IAM credentials (e.g. using SSO to get temporary credentials).

https://github.com/aws/amazon-neptune-gremlin-dotnet-sigv4/blob/7a903ac0e28df2e1e6520add3197f3429c3a3693/src/SigV4RequestSigner.cs#L81-L87

Since Sign() does set the session token if one is provided, the fix should be straightforward:

var signedrequest = this.Sign(request, "neptune-db", _region, _token);
return new Action<ClientWebSocketOptions>(options => {
    options.SetRequestHeader("host", neptune_endpoint);
    options.SetRequestHeader("x-amz-date", signedrequest.Headers.GetValues("x-amz-date").FirstOrDefault());
    options.SetRequestHeader("x-amz-security-token", signedrequest.Headers.GetValues("x-amz-security-token").FirstOrDefault());
    options.SetRequestHeader("Authorization", signedrequest.Headers.GetValues("Authorization").FirstOrDefault());

aws / amazon-neptune-gremlin-dotnet-sigv4

Session token is missing from signed request headers #1