title: Native login page with IdentityServer4 authorization code flow
body: <p>I'm building a mobile application with Xamarin forms.
  As part of the application i need to be able to authorize/authenticate users.
  I am using IdentityServer4 and asp.net to achieve that.
  From what i understand the recommended approach today is to use authorization code flow + PKCE.
  There is only one problem with that, i don't want to redirect users to a login page on identityserver, i want the login page to be a native login page on the application.
  How can i achieve that and still use authorization code flow?
  Help would be appreciated.</p>