### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

We are using the `Authorization` header for routing purposes

```
 "authorization: AWS4-HMAC-SHA256 <...>"
```

https://github.com/localstack/localstack/issues/5770

### Expected Behavior

Use a custom header to avoid causing confusion with backend integrations

### How are you starting LocalStack?

With a `docker run` command

### Steps To Reproduce

Run a custom HTTP integration without authorisation

### Environment

```markdown
- OS: 
- LocalStack:
```


### Anything else?

No
server_address=parsed_url.netloc,
        )
        return response
    ssl_creds = (None, None)
    if use_ssl:
        install_predefined_cert_if_available()
        _, cert_file_name, key_file_name = GenericProxy.create_ssl_cert(serial_number=port)
        ssl_creds = (cert_file_name, key_file_name)
    result = http2_server.run_server(
        port,
        bind_address,
        handler=handler,
        asynchronous=asynchronous,
        ssl_creds=ssl_creds,
        max_content_length=max_content_length,
        send_timeout=send_timeout,
    )
    if asynchronous and check_port:
        wait_for_port_open(port, sleep_time=0.2, retries=12)
    return result
def install_predefined_cert_if_available():
    try:
        from localstack_ext.bootstrap import install
        if config.SKIP_SSL_CERT_DOWNLOAD:
            LOG.debug("Skipping download of local SSL cert, as SKIP_SSL_CERT_DOWNLOAD=1")
            return
        install.setup_ssl_cert()
    except Exception:
        pass
def serve_flask_app(app, port, host=None, cors=True, asynchronous=False):