### 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
return self._url.geturl()
    def do_run(self):
        self.endpoint.register()
        try:
            self._shutdown_event.wait()
        finally:
            self.endpoint.unregister()
    def do_shutdown(self):
        self._shutdown_event.set()
        self.endpoint.unregister()
async def _accept_connection2(self, protocol_factory, conn, extra, sslcontext, *args, **kwargs):
    is_ssl_socket = DuplexSocket.is_ssl_socket(conn)
    if is_ssl_socket is False:
        sslcontext = None
    result = await _accept_connection2_orig(
        self, protocol_factory, conn, extra, sslcontext, *args, **kwargs
    )
    return result
if hasattr(BaseSelectorEventLoop, "_accept_connection2") and not hasattr(
    BaseSelectorEventLoop, "_ls_patched"
):
    _accept_connection2_orig = BaseSelectorEventLoop._accept_connection2
    BaseSelectorEventLoop._accept_connection2 = _accept_connection2
    BaseSelectorEventLoop._ls_patched = True
def get_cert_pem_file_path():