title: Adding a parameter to the post-logout redirect
body: <p>We're using IdentityServer4 for access control to a .net core 3 MVC application (we'll be adding a single page application later as well) where we've got a unique identifier as a parameter for the initial login page. 
  How can we get the the post logout redirect to get back to the login page with the parameter from the previous login?
  Thanks</p>