Build fix.

src/Squidex/Areas/IdentityServer/Config/IdentityServerExtensions.cs

@@ -12,6 +12,7 @@ using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.Extensions.DependencyInjection;
 using Microsoft.Extensions.Options;
+using Microsoft.IdentityModel.Logging;
 using Squidex.Config;
 using Squidex.Domain.Users;
 using Squidex.Infrastructure.Log;