Never remove exercises that are part of an evaluation

app/jobs/remove_activities_job.rb

@@ -2,6 +2,7 @@ class RemoveActivitiesJob < ApplicationJob
   # permanently remove activities that match all of the following criteria:
   # - status is 'removed'
   # - updated_at is more than 1 month ago
+  # - not part of an evaluation
   # - one of the following is true:
   #   - draft is true (never published)
   #   - series_memberships is empty and less then 25 submissions and latest submission is more than 1 month ago
@@ -28,6 +29,8 @@ def perform
         next if activity.submissions.present? && activity.submissions.reorder(:created_at).last.created_at > 1.month.ago
       end
 
+      next if EvaluationExercise.exists?(exercise_id: activity.id)
+
       # destroy submissions first explicitly, as they are dependent: :restrict_with_error
       activity.submissions.destroy_all