User defined key attribute on Cart Discount

Added the key attribute to CartDiscount. You can use the key attribute when creating or updating a CartDiscount.

• [API] Added the key attribute to the CartDiscount and CartDiscountDraft representations.
• [API] Added the Get CartDiscount by Key, Update CartDiscount by Key, and Delete CartDiscount by Key endpoints.
• [GraphQL API] The GraphQL API now supports queries and mutations of CartDiscount by the key attribute.
• [GraphQL API] Added the following types to the GraphQL schema: SetCartDiscountKey.
• [GraphQL API] Changed the CartDiscountDraft type:
  • Input field key was added to CartDiscountDraft type
• [GraphQL API] Changed the Query type:
  • Query.cartDiscount(id) description is changed
  • Argument key was added to Query.cartDiscount field
  • Query.cartDiscount(id) type changed from String! to String
• [GraphQL API] Changed the CartDiscount type:
  • Added the key field to the CartDiscount type.
• [GraphQL API] Changed the CartDiscountUpdateAction type:
  • Input field setKey was added to CartDiscountUpdateAction type
• [GraphQL API] Changed the Mutation type:
  • Mutation.updateCartDiscount(id) type changed from String! to String
  • Mutation.deleteCartDiscount(id) description is changed
  • Argument key was added to Mutation.updateCartDiscount field
  • Mutation.deleteCartDiscount(id) type changed from String! to String
  • Argument key was added to Mutation.deleteCartDiscount field
  • Mutation.updateCartDiscount(id) description is changed

Introduced the following changes to the GraphQL schema (in SDL format):

extend type CartDiscount {
  key: String
}

extend input CartDiscountDraft {
  key: String
}

extend input CartDiscountUpdateAction {
  setKey: SetCartDiscountKey
}

input SetCartDiscountKey {
  key: String
}