Adds support for return shipping methods and changes returns to have a request/receive flow. Store operators should now first request a return, noting the line items that will be returned. When the inventory is received the return will be registered triggering the refund. Return shipping methods can now be created for all regions.
Adds ShippingProfiles:
With Shipping Profiles store operators can group products together and select which shipping options can fulfill the products. The shipping profiles are region agnostic, but for products to be shippable to a given region the shipping profile must have a shipping option associated that ships to this region.
Adds Shipping Options:
Shipping Options represents a way that the customer can have their order shipped. The shipping option has a fulfillment provider associated to determine who fulfills orders with the given shipping method. If a fulfillment provider has multiple ways that they can ship a shipping option for each of the fulfillment provider's shipping options can be created.
