Implement orders

[vernondegoede]

• [x] Create order
  • [x] Add shipping costs
  • [x] Add line items
  • [x] Handle line item discounts
  • [x] Handle order discounts
  • [x] Fetch payments methods for order resource using currency and order amount
  • [x] Refactor MoneyFormatter to a Rails Concern
  • [x] Implement OrderSerializer abstraction
  • [x] Cancel previous Mollie Orders when starting a payment in Spree (aka when creating a new Mollie order)
• [x] Order state updates
  • [x] Implement custom Spree::Mollie::PaymentStateUpdater which handles payment state updates
  • [x] Set correct Spree order state when payment is authorized
  • [x] Set correct Spree order state when payment is paid
  • [x] Only send order confirmation if its not delivered yet and payment is paid? or authorized?
  • [x] Use correct payment state while processing (started_processing!
  • [x] Use correct payment state for authorized orders (pend!)
• [x] Shipments
  • [x] Create new Mollie Shipment when shipment is created through Spree
  • [x] Collect shipping fees and discounts after first shipment
• [x] Order cancelations
• [x] Order details in Spree admin

[vernondegoede]

Will pick up existing tasks in #42 and #41.