WIP: Products may be created with pounds for their weight unit_converter

See: https://community.openfoodnetwork.org/t/hubs-managers-can-choose-the-adapted-weight-and-measure-units-for-their-shops-given-their-own-local-situation/1289/11

We're not entirely sure what needs to be changed in order for this to
accurately work with shipping and other parts of the eCommerce platform.

We are assuming that so long as we canonically store the weight scale
in grams, that the shipping calculation will be able to do what it needs
to. So if we put in values for "oz" as grams, we may not need to do
much else in order to let product(s) be sold by the pound (or ounce).

Next steps appear to be:

- [ ] When looking at an order as a customer, do we want to show pounds
      instead of grams? (See: http://localhost:3000/orders/R125684626)
- [ ] Compile a list of tests that are worth writing (because we have
      no confidence that we know what we are supposed to be doing in
      order for this feature to be "ready" to be used by people.)
- [ ] Write a test that demonstrates when we create a product with a
      variant in pound that the product's shipping weight is correctly
      calculated?
- [ ] Do we want to think about i18n?

app/assets/javascripts/admin/products/services/variant_unit_manager.js.coffee

@@ -4,7 +4,15 @@ angular.module("admin.products").factory "VariantUnitManager", ->
       'weight':
         1.0: 'g'
         1000.0: 'kg'
-        1000000.0: 'T'
+        1000000.0: 'T',
+        # This appears to be what needs to be set in order for
+        # products to have a mass value stored in the database
+        # when they are created. However, it does not appear to
+        # change the existing product(s), so if the scale value
+        # is changed, a data migration may be necessary to make sure
+        # the proper unit X to grams actually works.
+        # TODO: ^^^ Delete this
+        453.592: 'lb'
       'volume':
         0.001: 'mL'
         1.0: 'L'