Add list repository. The repository is an interface to the database and handles mapping entities (pure Ruby objects) to data models (Mongoid documents)
user
```ruby
module ListRepository
  extend self

  def find_by_date(date)
    ListData.where(date: date)
  end

  def create_empty(title, date)
    ListData.create(title: title, date: date)
  end
end
```
assistant