only library involved is libc.so, which can usually be assumed
present.)

This conflict between functionality and the gcc requirement means we
must support both internal and external linking, depending on the
circumstances: if net is the only cgo-using package, then internal
linking is probably fine, but if other packages are involved, so that there

    description: str
    paid: bool


class InvoiceEventReceived(BaseModel):
    ok: bool


invoices_callback_router = APIRouter()


@invoices_callback_router.post(
    "{$callback_url}/invoices/{$request.body.id}", response_model=InvoiceEventReceived
)
def invoice_notification(body: InvoiceEvent):
    pass  # pragma: nocover


class Event(BaseModel):
    name: str
    total: float

    ok: bool


invoices_callback_router = APIRouter()


@invoices_callback_router.post(
    "{$callback_url}/invoices/{$request.body.id}", response_model=InvoiceEventReceived
)
def invoice_notification(body: InvoiceEvent):
    pass


@app.post("/invoices/", callbacks=invoices_callback_router.routes)
def create_invoice(invoice: Invoice, callback_url: HttpUrl | None = None):
    """
    Create an invoice.

Bu örnekte, bu bir `str`:

```Python
"{$callback_url}/invoices/{$request.body.id}"
```

Yani API'nizin kullanıcısı (external geliştirici) sizin API'nize şu adrese bir request gönderirse:

```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

ve JSON body şu şekilde olursa:

```JSON
{

В нашем случае это `str`:

```Python
"{$callback_url}/invoices/{$request.body.id}"
```

Итак, если пользователь вашего API (внешний разработчик) отправляет HTTP-запрос вашему API по адресу:

```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

с телом JSON:

```JSON
{
    "id": "2expen51ve",

En este caso, es el `str`:

```Python
"{$callback_url}/invoices/{$request.body.id}"
```

Entonces, si el usuario de tu API (el desarrollador externo) envía un request a *tu API* a:

```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

con un JSON body de:

```JSON
{
    "id": "2expen51ve",

In diesem Fall ist es der `str`:

```Python
"{$callback_url}/invoices/{$request.body.id}"
```

Wenn Ihr API-Benutzer (der externe Entwickler) also einen Request an *Ihre API* sendet, via:

```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

mit einem JSON-Körper:

```JSON
{
    "id": "2expen51ve",

    // ThreadLocal is not available to GWT, so we always reuse the same
    // instance.  It is always safe to return the same instance because
    // javascript is single-threaded, and only used by blocks that doesn't
    // involve async callbacks.
    return CHAR_BUFFER;
  }

  private Platform() {}

## An app with callbacks { #an-app-with-callbacks }

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

These invoices will have an `id`, `title` (optional), `customer`, and `total`.

The user of your API (an external developer) will create an invoice in your API with a POST request.

Then your API will (let's imagine):

在這個例子中，它是一個 `str`：

```Python
"{$callback_url}/invoices/{$request.body.id}"
```

所以，如果你的 API 使用者（外部開發者）向「你的 API」送出這樣的請求：

```
https://yourapi.com/invoices/?callback_url=https://www.external.org/events
```

並附上這個 JSON body：

```JSON
{
    "id": "2expen51ve",
    "customer": "Mr. Richie Rich",