[FEAT] Fix IdpOptions when loading

[eByte23]

When loading idp metadata you shouldn't then have to re-find that same idp to set the settings for it

//Currently
   var myconfig = new Saml2Configuration
        {
            ServiceProvider = new ServiceProvider
            {
                SigningCertificate = new X509Certificate2(FileEmbeddedResource("cert.pfx"), "pass", MachineKeySet),
                Server = "https://localhost:44333/myapp",
                Id = "https://localhost:44333/myapp"       // EntityId used in SAMLP to identify this SP
            },
            AllowedAudienceUris = new List<Uri>(new[] { new Uri("https://localhost:44333/myapp") })
        };
        myconfig.ServiceProvider.Endpoints.AddRange(new[] {
            new ServiceProviderEndpoint(EndpointType.SignOn, "/myapp/saml2/login", "/core"),
            new ServiceProviderEndpoint(EndpointType.Logout, "/myapp/saml2/logout", "/core"),
            new ServiceProviderEndpoint(EndpointType.Metadata, "/myapp/saml2/metadata")
        });
        myconfig.IdentityProviders.AddByMetadata("IdPMetadataFile.xml");
        myconfig.IdentityProviders.First().OmitAssertionSignatureCheck = true;
        myconfig.LoggingFactoryType = "SAML2.Logging.DebugLoggerFactory";
        return myconfig;

We should

   var myconfig = new Saml2Configuration
        {
            ServiceProvider = new ServiceProvider
            {
                SigningCertificate = new X509Certificate2(FileEmbeddedResource("cert.pfx"), "pass", MachineKeySet),
                Server = "https://localhost:44333/myapp",
                Id = "https://localhost:44333/myapp"       // EntityId used in SAMLP to identify this SP
            },
            AllowedAudienceUris = new List<Uri>(new[] { new Uri("https://localhost:44333/myapp") })
        };

        myconfig.ServiceProvider.Endpoints.AddRange(new[] {
            new ServiceProviderEndpoint(EndpointType.SignOn, "/myapp/saml2/login", "/core"),
            new ServiceProviderEndpoint(EndpointType.Logout, "/myapp/saml2/logout", "/core"),
            new ServiceProviderEndpoint(EndpointType.Metadata, "/myapp/saml2/metadata")
        });
        myconfig.IdentityProviders.AddByMetadata("IdPMetadataFile.xml", new IdentityProviderOptions 
        {
           OmitAssertionSignatureCheck = true
        });
        myconfig.LoggingFactoryType = "SAML2.Logging.DebugLoggerFactory";
        return myconfig;