Task: build a API for maintaining a shopping cart in Python using Django.

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:

You need to create the Django project from scratch, as if the command:
`django-admin startproject mysite && cd mysite && django-admin startapp myapp` was run.

You need to create the following files:
mysite/asgi.py
mysite/wsgi.py
mysite/settings.py
mysite/urls.py
mysite/__init__.py
manage.py
myapp/tests.py
myapp/admin.py
myapp/apps.py
myapp/models.py
myapp/views.py
myapp/urls.py
myapp/__init__.py
myapp/migrations/__init__.py


Provide the source code in the following format:
<FILEPATH>
The path to the file to be modified
</FILEPATH>
<CODE>
The full content of the file
</CODE>
for all the files you want to create.

Example:
<FILEPATH>
path/to/file.py
</FILEPATH>
<CODE>
def hello_world():
    pass
</CODE>



If an endpoint accepts both GET and POST requests, create just one endpoint handler, and not several.
Make sure that the endpoints don't have trailing slashes!
Set the ALLOWED_HOSTS to ["0.0.0.0", "localhost", "127.0.0.1"]
Make sure that the command `python manage.py runserver` starts the app successfully.


Allowed packages:

asgiref==3.8.1
Django==5.1.4
sqlparse==0.5.3
pyjwt==2.10.0