Migration guide for v8

Deprecated

• The save method is deprecated. Prefer the static update method that doesn't require retrieval of the resource to update it.

  # before
  refund = Stripe::Refund.retrieve("re_123")
  refund.description = "Refund description"
  refund.save
  
  # after
  Stripe::Refund.update("re_123", description: "Refund description")