Please add Forms & ASP.NET Impersonation Authentication in WebApplication & WebSite.  For WebApplication https://github.com/dsccommunity/WebAdministrationDsc/blob/db3d024d954f00268af9ae5be2a720789301da24/source/DSCResources/DSC_WebApplication/DSC_WebApplication.psm1#L570 For WebSite: https://github.com/dsccommunity/WebAdministrationDsc/blob/db3d024d954f00268af9ae5be2a720789301da24/source/DSCResources/DSC_WebSite/DSC_WebSite.psm1#L1673