Add APIGateway example to aws-sig-auth (#1020)

//! AWS Signature Authentication Package

//!

//! This crate may be used to generate presigned URLs for unmodeled behavior such as `rds-iam-token`.

//! This crate may be used to generate presigned URLs for unmodeled behavior such as `rds-iam-token`

//! or to sign requests to APIGateway-based services with IAM authorization.

//!

//! # Examples

//!

//! Generate RDS IAM Token:

//! ## Generate RDS IAM Token

//! ```rust

//! use aws_smithy_http::body::SdkBody;

//! use aws_types::region::{Region, SigningRegion};

//! # // validate against token generated by the aws CLI

//! # assert_eq!(token, "prod-instance.us-east-1.rds.amazonaws.com:3306/?Action=connect&DBUser=dbuser&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIDEXAMPLE%2F20211026%2Fus-east-1%2Frds-db%2Faws4_request&X-Amz-Date=20211026T140940Z&X-Amz-Expires=900&X-Amz-SignedHeaders=host&X-Amz-Signature=9632f5f4fcd2087a3c523f55f72d2fe97fad03b71a0a23b8c1edfb104e8072d1");

//! ```

//!

//! ## Sign a request for APIGateway execute-api

//!

//! ```no_run

//! use aws_sig_auth::signer::{OperationSigningConfig, RequestConfig, SigV4Signer};

//! use aws_smithy_http::body::SdkBody;

//! use aws_types::credentials::ProvideCredentials;

//! use aws_types::region::{Region, SigningRegion};

//! use aws_types::SigningService;

//! use std::error::Error;

//! use std::time::SystemTime;

//! async fn sign_request(

//!     mut request: &mut http::Request<SdkBody>,

//!     region: Region,

//!     credentials_provider: &impl ProvideCredentials,

//! ) -> Result<(), Box<dyn Error + Send + Sync>> {

//!     let now = SystemTime::now();

//!     let signer = SigV4Signer::new();

//!     let request_config = RequestConfig {

//!         request_ts: now,

//!         region: &SigningRegion::from(region),

//!         service: &SigningService::from_static("execute-api"),

//!         payload_override: None,

//!     };

//!     signer.sign(

//!         &OperationSigningConfig::default_config(),

//!         &request_config,

//!         &credentials_provider.provide_credentials().await?,

//!         &mut request,

//!     )?;

//!     Ok((()))

//! }

//! ```

#[cfg(feature = "sign-eventstream")]

pub mod event_stream;