public static IIdentityServiceBuilder AddSigningCertificates(
            this IIdentityServiceBuilder builder,
            IEnumerable <X509Certificate2> certificates)
        {
            foreach (var certificate in certificates)
            {
                builder.AddSigningCertificate(certificate);
            }

            return(builder);
        }
        public static IIdentityServiceBuilder AddSigningCertificate(this IIdentityServiceBuilder builder, Func <X509Certificate2> func)
        {
            var cert = func();

            if (cert == null)
            {
                return(builder);
            }
            else
            {
                return(builder.AddSigningCertificate(cert));
            }
        }