I inherited an app that is using ITfoxtec.Identity.Saml2 to authenticate with an identity/oidc provider using SAML 2.0.

I haven’t been able to figure out how to configure and send additional params when authenticating with the identity provider. Any help or pointers appreciated, tyia

Our provider requires us to send two params, PartnerSpID and an ACS index. e.g.
https://my.oid.provider.com/idp/provider.saml2?partnerspid=abc&acsidx=1

The app is configuring SAML Auth with ITfoxtec SAML library like:

IServiceCollection services = ...

services.AddRazorPages();
services.Configure<Saml2Configuration>(Configuration.GetSection("SamlAuth"));

services.Configure<Saml2Configuration>(saml2Configuration =>
{
    saml2Configuration.AllowedAudienceUris.Add(saml2Configuration.Issuer);

    var entityDescriptor = new EntityDescriptor();
    entityDescriptor.ReadIdPSsoDescriptorFromUrl(new Uri(Configuration["SamlAuth:IdPMetadata"]));

    if (entityDescriptor.IdPSsoDescriptor != null)
    {
        saml2Configuration.SingleSignOnDestination = entityDescriptor.IdPSsoDescriptor.SingleSignOnServices.First().Location;
        saml2Configuration.SignatureValidationCertificates.AddRange(entityDescriptor.IdPSsoDescriptor.SigningCertificates);
    }
    else
    {
        // fail fast...
    }
});

services.AddSaml2();