```ruby
class SystemRole
  BASIC = 'basic'
  ADMIN = 'admin'

  ROLES = [BASIC, ADMIN]
end```

Replace 'BASIC' role with Convenor, Tutor, and Student system roles.
user
```ruby
class SystemRole
  ADMIN = 'admin'
  CONVENOR = 'convenor'
  TUTOR = 'tutor'
  STUDENT = 'student'

  ROLES = [ADMIN, CONVENOR, TUTOR, STUDENT]
end```
assistant