In this case, you could want to document how that external API *should* look like. What *path operation* it should have, what body it should expect, what response it should return, etc.

## An app with callbacks

Let's see all this with an example.

Imagine you develop an app that allows creating invoices.

To achieve this, the `:80`-backend must have a list of "allowed origins".

In this case, the list would have to include `http://localhost:8080` for the `:8080`-frontend to work correctly.

    constructor(response: Response) {
      this.url = response.request.url
      this.varyHeaders = response.varyHeaders()
      this.requestMethod = response.request.method
      this.protocol = response.protocol
      this.code = response.code
      this.message = response.message
      this.responseHeaders = response.headers
      this.handshake = response.handshake
      this.sentRequestMillis = response.sentRequestAtMillis

/**
 * Static methods pertaining to ASCII characters (those in the range of values {@code 0x00} through
 * {@code 0x7F}), and to strings containing such characters.
 *
 * <p>ASCII utilities also exist in other classes of this package:
 *
 * <ul>
 *   <!-- TODO(kevinb): how can we make this not produce a warning when building gwt javadoc? -->
 *   <li>{@link StandardCharsets#US_ASCII} specifies the {@code Charset} of ASCII characters.

## Usar `CORSMiddleware`

Você pode configurá-lo em sua aplicação **FastAPI** usando o `CORSMiddleware`.

* Importe `CORSMiddleware`.
* Crie uma lista de origens permitidas (como strings).
* Adicione-a como um "middleware" à sua aplicação **FastAPI**.

Você também pode especificar se o seu backend permite:

* Credenciais (Cabeçalhos de autorização, Cookies, etc).

```
http://127.0.0.1:8000/items/?skip=0&limit=10
```

...the query parameters are:

* `skip`: with a value of `0`
* `limit`: with a value of `10`

As they are part of the URL, they are "naturally" strings.

But when you declare them with Python types (in the example above, as `int`), they are converted to that type and validated against it.

All the same process that applied for path parameters also applies for query parameters:

// Copyright (c) 2015-2023 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful

For example, the `PATH` environment variable could look like this:

//// tab | Linux, macOS

```plaintext
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin
```

This means that the system should look for programs in the directories:

* `/usr/local/bin`
* `/usr/bin`
* `/bin`
* `/usr/sbin`
* `/sbin`

////

        this.repoSystem = repoSystem;
        this.settingsDecrypter = settingsDecrypter;
        this.eventSpyDispatcher = eventSpyDispatcher;
        this.runtimeInformation = runtimeInformation;
        this.typeRegistry = typeRegistry;
        this.versionScheme = versionScheme;
        this.requestExtenders = requestExtenders;
        this.sessionExtenders = sessionExtenders;
    }

	// activity initiated from this cluster
	ReplicationStatus = "replication-status"
	// ReplicationTimestamp - the last time replication was initiated on this cluster for this object version
	ReplicationTimestamp = "replication-timestamp"
	// ReplicaStatus - this header is present if a replica was received by this cluster for this object version
	ReplicaStatus = "replica-status"