Added 'key' to Cart Line Item

We introduced the key field on LineItem and LineItemDraft. This ensures a consistent experience when working with external identifiers across different entity types in Composable Commerce.

Changes:

• [GraphQL API] Changed the AddStagedOrderLineItem type:
  • Input field key was added to AddStagedOrderLineItem type
• [GraphQL API] Changed the MyLineItemDraft type:
  • Input field key was added to MyLineItemDraft type
• [GraphQL API] Changed the LineItemDraft type:
  • Input field key was added to LineItemDraft type
• [GraphQL API] Changed the AddCartLineItem type:
  • Input field key was added to AddCartLineItem type
• [GraphQL API] Changed the LineItem type:
  • Added the key field to the LineItem type.
• [GraphQL API] Changed the LineItemDraftOutput type:
  • Added the key field to the LineItemDraftOutput type.
• [GraphQL API] Changed the AddMyCartLineItem type:
  • Input field key was added to AddMyCartLineItem type

The following changes were introduced in terms of GraphQL SDL:

extend type LineItemDraftOutput {
  key: String
}

extend type LineItem {
  key: String
}

extend input AddMyCartLineItem {
  key: String
}

extend input AddStagedOrderLineItem {
  key: String
}

extend input MyLineItemDraft {
  key: String
}

extend input LineItemDraft {
  key: String
}

extend input AddCartLineItem {
  key: String
}