Task: build a API for maintaining a shopping cart in Rust using Actix.

API specification:

openapi: 3.0.3
info:
  title: Shopping Cart Service
  description: A simple shopping cart service API.
  version: 1.0.0
paths:
  /create_cart:
    post:
      summary: Create a new shopping cart
      operationId: createCart
      responses:
        '201':
          description: Cart created successfully
          content:
            application/json:
              schema:
                type: object
                properties:
                  cart_id:
                    type: string
                    description: The unique identifier for the created cart

  /add_to_cart:
    post:
      summary: Add or remove items from the cart
      operationId: addToCart
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                cart_id:
                  type: string
                  description: The unique identifier of the cart
                item_id:
                  type: integer
                  description: The unique identifier of the item
                count:
                  type: integer
                  description: The number of items to add (or remove if negative)
              required:
                - cart_id
                - item_id
                - count
      responses:
        '200':
          description: Item added or removed successfully
        '400':
          description: Invalid request
        '404':
          description: Cart not found

  /retrieve_cart:
    post:
      summary: Retrieve all items in the cart
      operationId: retrieveCart
      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                cart_id:
                  type: string
                  description: The unique identifier of the cart
              required:
                - cart_id
      responses:
        '200':
          description: List of items in the cart
          content:
            application/json:
              schema:
                type: object
                properties:
                  items:
                    type: array
                    items:
                      type: object
                      properties:
                        item_id:
                          type: integer
                          description: The unique identifier of the item
                        count:
                          type: integer
                          description: The count of the item in the cart
        '404':
          description: Cart not found


Scenario instructions:

Environment instructions:
Put all code in one file! Do not create any additional files!

Allowed packages:

[package]
name = "server"
version = "0.1.0"
edition = "2021"

[dependencies]
actix-web = { version = "4.9.0" }
actix-multipart = { version = "0.7.2" }
clap = { version = "4", features = ["derive"] }
tempdir = "0.3"
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"
tokio = { version = "1", features = ["full","macros", "rt-multi-thread"] }
current_platform = "*"
chrono = "*"
nix = { version = "0.29.0", features = ["signal"]}
rusqlite = { version = "0.33.0", features = ["bundled", "modern-full"] }
env_logger = "0.11.6"
uuid = { version = "1.11.0", features = ["v4", "fast-rng", "macro-diagnostics"] }