Show paste if one has completed similar exercise

Not the perfect solution but should be fine for now

Author: nygrenh

app/controllers/submissions_controller.rb

@@ -315,6 +315,7 @@ def check_access!
       end
 
       paste_visible = @submission.paste_visible_for?(current_user)
+      return if paste_visible
       paste_visibility = @course.paste_visibility || 'open'
       case paste_visibility
       when 'protected'

app/models/submission.rb

@@ -346,6 +346,7 @@ def self.eager_load_exercises(submissions)
   def paste_visible_for?(user)
     return false unless paste_available
     return true if exercise && exercise.completed_by?(user)
+    return true if user.submissions.where(exercise_name: exercise.name, pretest_error: nil, all_tests_passed: true).any?
     !all_tests_passed
   end