Filtered "top of the group" has_many association with a :through conterpart

model.rb

  scope :latest_prices, lambda {
    joins('
          LEFT JOIN client_products filter
          ON filter.product_id = "client_products"."product_id"
          AND "client_products"."created_at" < filter.created_at')
      .where('filter.id IS NULL')
      .where('"client_products"."price_per_pack" > 0')
  }

  has_many :client_products, -> { merge Client.latest_prices }
  has_many :products, -> { merge Client.latest_prices }, through: :client_products