Fix courses specs after auth inclusion
Fix exams specs after auth inclusion
Fix extracurricular_activities specs after auth inclusion
Fix syllabuses specs after auth inclusion
Fix controller specs
Fix model specs
Fix some request specs
Create permission checks via ensures
Fix spec/controllers/gaku/class_group_enrollments_controller_spec
Delete empty controller specs
Delete test folder
Delete mailers directory
Clean Ability and AdminAbility
Create ensures "deny except" shared example