Added 'oldValue' field to Standalone Price Value Changed Message

We added the oldValue field to the Standalone Price Value Changed Message that contains the StandalonePrice value as it was before the change. You can now see how much the value of your updated Standalone Price has changed by comparing the Message fields value and oldValue.

Changes:

• [API] Added field oldValue to Standalone Price Value Changed Message.
• [GraphQL API] Changed the StandalonePriceValueChanged type:
  • Added the oldValue field to the StandalonePriceValueChanged type.

The following changes were introduced in terms of GraphQL SDL:

extend type StandalonePriceValueChanged {
  oldValue: BaseMoney
}