FormDescriptor formDescriptor = new FormDescriptor
{
    SendToMeEmail =  "info@mercator.eu",
    FileName = "myinvoice.pdf",
    Fields = new List<FormDescriptor.Field>
    {
        new FormDescriptor.Field
        {
            Marker = "Signature_1",
            InputType = "CanvasSIG",
            Name = "SIG_FIELD_1",
            Required = true,
            Width = 175,
            Height = 70,
            SignerId = "bt_00000000-0000-0000-0000-000000000001",
            SigningOptions = new FormDescriptor.Signingoptions
            {
                Eid = new FormDescriptor.Eid(),
                Pen = new FormDescriptor.Pen(),
                Tan = new FormDescriptor.Tan(),
                //Itsme = new FormDescriptor.Itsme()
            }
        }
    },
    SignersInfo = new List<FormDescriptor.Signersinfo>
    {
        new FormDescriptor.Signersinfo
        {
            Name = "Jules Leboss",
            Mobile = "+32499799999",
            ActingAs = "Administrateur",
            Id = "bt_00000000-0000-0000-0000-000000000001",
            Email = "jules.leboss@company.com"
        }
    }
};