Add events for pair programming study

app/controllers/exercises_controller.rb

@@ -315,6 +315,8 @@ class ExercisesController < ApplicationController
       # we are just acting on behalf of a single user who has already worked on this exercise as part of a programming group **in the context of the current study group**
       session[:pg_id] = pg.id
       @current_contributor = pg
+    elsif PairProgramming23Study.participate?(current_user, @exercise) && current_user.submissions.where(study_group_id: current_user.current_study_group_id, exercise: @exercise).any?
+      Event.create(category: 'pp_work_alone', user: current_user, exercise: @exercise, data: nil, file_id: nil)
     end
 
     user_solved_exercise = @exercise.solved_by?(current_contributor)