"""
    Create an invoice.

    This will (let's imagine) let the API user (some external developer) create an
    invoice.

    And this path operation will:

    * Send the invoice to the client.
    * Collect the money from the client.
    * Send a notification back to the API user (the external developer), as a callback.
        * At this point is that the API will somehow send a POST request to the

```Python hl_lines="3-16  18"
{!../../../docs_src/metadata/tutorial004.py!}
```

Notice that you can use Markdown inside of the descriptions, for example "login" will be shown in bold (**login**) and "fancy" will be shown in italics (_fancy_).

!!! tip
    You don't have to add metadata for all the tags that you use.

### Use your tags

Hiding your documentation user interfaces in production *shouldn't* be the way to protect your API.

That doesn't add any extra security to your API, the *path operations* will still be available where they are.

If there's a security flaw in your code, it will still exist.

    ```

The files and form fields will be uploaded as form data and you will receive the files and form fields.

And you can declare some of the files as `bytes` and some as `UploadFile`.

!!! warning

    These docs are about to be updated. 🎉

    The current version assumes Pydantic v1.

    The new docs will include Pydantic v2 and will use <a href="https://sqlmodel.tiangolo.com/" class="external-link" target="_blank">SQLModel</a> once it is updated to use Pydantic v2 as well.

!!! warning "Deprecated"
    This tutorial is deprecated and will be removed in a future version.

Similar to the way you can [add `dependencies` to the *path operation decorators*](dependencies-in-path-operation-decorators.md){.internal-link target=_blank}, you can add them to the `FastAPI` application.

In that case, they will be applied to all the *path operations* in the application:

=== "Python 3.9+"

    ```Python hl_lines="16"
    {!> ../../../docs_src/dependencies/tutorial012_an_py39.py!}
    ```

=== "Python 3.8+"

```

By declaring a *path operation function* parameter with the type being the `Request` **FastAPI** will know to pass the `Request` in that parameter.

!!! tip
    Note that in this case, we are declaring a path parameter beside the request parameter.

    So, the path parameter will be extracted, validated, converted to the specified type and annotated with OpenAPI.

            "title": "ChimichangApp",
            "summary": "Deadpool's favorite app. Nuff said.",
            "description": "\nChimichangApp API helps you do awesome stuff. 🚀\n\n## Items\n\nYou can **read items**.\n\n## Users\n\nYou will be able to:\n\n* **Create users** (_not implemented_).\n* **Read users** (_not implemented_).\n",
            "termsOfService": "http://example.com/terms/",
            "contact": {
                "name": "Deadpoolio the Amazing",

    'ignore:The loop argument is deprecated since Python 3\.8, and scheduled for removal in Python 3\.10:DeprecationWarning:asyncio',
    'ignore:starlette.middleware.wsgi is deprecated and will be removed in a future release\..*:DeprecationWarning:starlette',
    # TODO: remove after upgrading HTTPX to a version newer than 0.23.0
    # Including PR: https://github.com/encode/httpx/pull/2309

    * This will be done by sending a POST request (from *your API*) to some *external API* provided by that external developer (this is the "callback").

## The normal **FastAPI** app

Let's first see how the normal API app would look like before adding the callback.

It will have a *path operation* that will receive an `Invoice` body, and a query parameter `callback_url` that will contain the URL for the callback.