Routes helpers available inside ArraySerializer

I'm trying to do something like this:
```ruby
class TasksSerializer < ActiveModel::ArraySerializer

  self.root = false

  def as_json(*args)
    {
      _results: super,
      _links: links
    }
  end

  def links
    {
      tasks: tasks_url
    }
  end
end
```

So I need to use the route helper ``tasks_url``.

I'm not sure what is the best way to implement that, but here is my suggestion.