New `item_nickname` argument on `create

🏷️ API version: 2025-10

When creating a new board via the API, you can now set the item nickname configuration for items on a board using the item_nickname argument.

mutation {
  create_board(
    board_name: "my board",
    board_kind: public,
    item_nickname: { 
      preset_type: "item" 
    }
  ) { 
    id 
  }
}