Allow for shipping information to be pre-selected and used to calculate shipping prices before issuing a signature request

[Soleone]

• Imported manually from Trello card.
• Tagged as Feature Requests in Trello.
• Originally created on 2018-03-08

Originally created by @Soleone:

To clarify, the problem is that during checkouts on stores you usually provide your address first, and only then are you offered shipping rates. Picking the shipping rate will then adjust the price accordingly so only then can we send the payment transaction.