### 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
path=handler_chain_request.path,
            data=data_to_send or handler_chain_request.data,
            headers=headers_to_send or handler_chain_request.headers,
            response=response,
        )
        message_modifier = isinstance(listener, MessageModifyingProxyListener)
        if message_modifier and isinstance(updated_response, RoutingResponse):
            
            response.status_code = updated_response.status_code or response.status_code
            response.headers = updated_response.headers or response.headers
            if isinstance(updated_response.content, (str, bytes)):
                response._content = updated_response.content
        if isinstance(updated_response, Response):
            response = updated_response
    
    from localstack.services.s3.s3_listener import ProxyListenerS3
    is_s3_listener = any(
        isinstance(service_listener, ProxyListenerS3) for service_listener in listeners
    )
    if not is_s3_listener:
        append_cors_headers(request_headers=headers, response=response)
    return response
def build_x_forwarded_for(headers, client_address, server_address):
    x_forwarded_for = headers.get("X-Forwarded-For")
    if x_forwarded_for:
        x_forwarded_for_list = (x_forwarded_for, client_address, server_address)
    else:
        x_forwarded_for_list = (client_address, server_address)
    return ", ".join(x_forwarded_for_list)
class DuplexSocket(ssl.SSLSocket):