UmbracoOwinStandardStartup.cs

public class UmbracoStandardOwinStartup : UmbracoDefaultOwinStartup
    {
        private readonly static string clientId = ConfigurationManager.AppSettings["ida:ClientId"];
        private readonly static string aadInstance = ConfigurationManager.AppSettings["ida:AADInstance"];
        private readonly static string tenantId = ConfigurationManager.AppSettings["ida:TenantId"];
        private readonly static string authority = aadInstance + tenantId;
        private readonly static string loginUrl = ConfigurationManager.AppSettings["ida:PostLoginUrl"];

        public override void Configuration(IAppBuilder app)
        {
            //ensure the default options are configured
            base.Configuration(app);

            app.ConfigureBackOfficeAzureActiveDirectoryAuth(tenantId, clientId, loginUrl, new Guid(tenantId));
        }
    }