Add live dashboard for teachers in the context of an exercise

This commit also adds the fundamentals for ActionCable

app/controllers/exercises_controller.rb

@@ -7,7 +7,7 @@ class ExercisesController < ApplicationController
 
   before_action :handle_file_uploads, only: [:create, :update]
   before_action :set_execution_environments, only: [:create, :edit, :new, :update]
-  before_action :set_exercise_and_authorize, only: MEMBER_ACTIONS + [:clone, :implement, :working_times, :intervention, :search, :run, :statistics, :submit, :reload, :feedback]
+  before_action :set_exercise_and_authorize, only: MEMBER_ACTIONS + [:clone, :implement, :working_times, :intervention, :search, :run, :statistics, :submit, :reload, :feedback, :study_group_dashboard]
   before_action :set_external_user_and_authorize, only: [:statistics]
   before_action :set_file_types, only: [:create, :edit, :new, :update]
   before_action :set_course_token, only: [:implement]
@@ -475,4 +475,13 @@ class ExercisesController < ApplicationController
     end
   end
 
+  def study_group_dashboard
+    authorize!
+    @study_group_id = params[:study_group_id]
+    @request_for_comments = RequestForComment.
+            where(exercise: @exercise).includes(:submission).
+            where(submissions: {study_group_id: @study_group_id}).
+            order(created_at: :desc)
+  end
+
 end

app/controllers/request_for_comments_controller.rb

@@ -143,7 +143,7 @@ class RequestForCommentsController < ApplicationController
     # Never trust parameters from the scary internet, only allow the white list through.
     def request_for_comment_params
       # The study_group_id might not be present in the session (e.g. for internal users), resulting in session[:study_group_id] = nil which is intended.
-      params.require(:request_for_comment).permit(:exercise_id, :file_id, :question, :requested_at, :solved, :submission_id).merge(user_id: current_user.id, user_type: current_user.class.name, study_group_id: session[:study_group_id])
+      params.require(:request_for_comment).permit(:exercise_id, :file_id, :question, :requested_at, :solved, :submission_id).merge(user_id: current_user.id, user_type: current_user.class.name)
     end
 
     def comment_params

app/controllers/submissions_controller.rb

@@ -201,6 +201,8 @@ class SubmissionsController < ApplicationController
     save_run_output
 
     if @run_output.blank?
+      @raw_output ||= ''
+      @run_output ||= ''
       parse_message t('exercises.implement.no_output', timestamp: l(Time.now, format: :short)), 'stdout', tubesock
     end