Presenting a line item or variants options_text uses overriden values

This changes how we display the description of weight, but it doesn't
change the `Spree::OptionValue`s that are being created when someone
adds a product to their cart.

This takes us closer by making the UI look more correct; but it feels
odd compared to settiong the `Spree::OptionValue` to the correct
unit on creation.

But on the other hand, that could possibly make things worse for the
shipping calculation bits.

lib/open_food_network/variant_and_line_item_naming.rb

@@ -18,7 +18,18 @@ module OpenFoodNetwork
                    order("#{Spree::OptionType.table_name}.position asc")
                end
 
-      values.map(&:presentation).to_sentence(words_connector: ", ", two_words_connector: ", ")
+      values.map { |option_value| presentation(option_value) }.to_sentence(words_connector: ", ", two_words_connector: ", ")
+    end
+
+    def presentation(option_value)
+      if option_value.option_type.name == "unit_weight"
+        if has_attribute?(:display_as) && display_as.present?
+          return display_as
+        elsif respond_to?(:variant) && variant.present? && variant.respond_to?(:display_as) && variant.display_as.present?
+          return variant.display_as
+        end
+      end
+      option_value.presentation
     end
 
     def product_and_full_name
@@ -48,9 +59,13 @@ module OpenFoodNetwork
     end
 
     def unit_to_display
-      return options_text if !has_attribute?(:display_as) || display_as.blank?
-
-      display_as
+      if has_attribute?(:display_as) && display_as.present?
+        display_as
+      elsif respond_to?(:variant) && variant.present? && variant.respond_to?(:display_as) && variant.display_as.present?
+        variant.display_as
+      else
+        options_text
+      end
     end
 
     def update_units