### Internal

* 🔥 Cleanup after upgrade for Docs Previews GitHub Action. PR [#2248](https://github.com/tiangolo/fastapi/pull/2248) by [@tiangolo](https://github.com/tiangolo).
* 🐛 Fix CI docs preview, unzip docs. PR [#2246](https://github.com/tiangolo/fastapi/pull/2246) by [@tiangolo](https://github.com/tiangolo).

!!! info
    In the `open()` function, the `mode="a"` means "append", so, the line will be added after whatever is on that file, without overwriting the previous contents.

!!! tip
    Notice that in this case we are using a standard Python `open()` function that interacts with a file.

This means that it will end up finishing some of the last tabs' requests earlier than some of the previous ones.

And it was thoroughly tested at the design phase, before any implementation, to ensure it would work with all the editors.

There were even some changes to Pydantic itself to support this.

The previous screenshots were taken with <a href="https://code.visualstudio.com" class="external-link" target="_blank">Visual Studio Code</a>.

# Simple OAuth2 with Password and Bearer

Now let's build from the previous chapter and add the missing parts to have a complete security flow.

## Get the `username` and `password`

We are going to use **FastAPI** security utilities to get the `username` and `password`.

OAuth2 specifies that when using the "password flow" (that we are using) the client/user must send a `username` and `password` fields as form data.

    Because of that, versions of FastAPI previous to 0.99.0 still used versions of OpenAPI lower than 3.1.0.

### Pydantic and FastAPI `examples`

This could be especially useful during testing, as it's very easy to override a dependency with your own custom settings.

### The config file

Coming from the previous example, your `config.py` file could look like:

```Python hl_lines="10"
{!../../../docs_src/settings/app02/config.py!}
```

Notice that now we don't create a default instance `settings = Settings()`.

* **Document** the parameter in the OpenAPI schema *path operation* (so it will show up in the **automatic docs UI**)

## Alternative (old) `Query` as the default value

    * Database models.
    * ...and many more.
* Automatic interactive API documentation, including 2 alternative user interfaces:
    * Swagger UI.
    * ReDoc.

---

Coming back to the previous code example, **FastAPI** will:

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.

    * Database models.
    * ...and many more.
* Automatic interactive API documentation, including 2 alternative user interfaces:
    * Swagger UI.
    * ReDoc.

---

Coming back to the previous code example, **FastAPI** will:

* Validate that there is an `item_id` in the path for `GET` and `PUT` requests.
* Validate that the `item_id` is of type `int` for `GET` and `PUT` requests.