Enable user destruction

app/graphql/types/dossier_type.rb

@@ -54,7 +54,11 @@ module Types
     end
 
     def usager
-      Loaders::Record.for(User).load(object.user_id)
+      if object.user_deleted?
+        { email: object.user_email_for(:display), id: -1 }
+      else
+        Loaders::Record.for(User).load(object.user_id)
+      end
     end
 
     def groupe_instructeur