Add explicit #start_on/#end_on to Role, remove FutureRole, Role#delet…

…e_on

app/models/die_mitte/role.rb

@@ -28,7 +28,7 @@ def to_s_with_merkmal(format = :default) # rubocop:disable Metrics/MethodLength
 
     unless format == :short
       model_name += " (#{label})" if label?
-      model_name += " (#{formatted_delete_date})" if delete_on
+      model_name += " (#{formatted_delete_date})" if end_on
     end
 
     if format == :long