Middleware not woking

Hi, I'm trying to filter a JSON request using a middleware but It doesn't appear to be working.

A request like this will work just fine
```
{"username":"username","email":"test@email.com","password":"password","confirm_password":"password"}
```

But one like this will throw validation errors saying that the fields are required
```
{"data":{"attributes":{"username":"username","email":"test@email.com","password":"password","confirm_password":"password"},"type":"users"}}
```

I've got a middleware that is meant to filter out the `data` and `attributes` part of the object and leave the content, It looks like this

```
public function handle($request, Closure $next)
{
$input = $request->all();

if (isset($input['data']['attributes'])) {
$input = $input['data']['attributes'];

$request->replace($input);
\Log::info($request->all());
}

return $next($request);
}
```

That log you see in the above method logs out the response I'm looking for
```
[2017-05-22 06:32:03] local.INFO: array (
'username' => 'username',
'email' => 'test@email.com',
'password' => 'password',
'confirm_password' => 'password',
)
```

But I still get the error
```
{"error":{"message":"422 Unprocessable Entity","errors":{"username":["The username field is required."],"email":["The email field is required."],"password":["The password field is required."],"confirm_password":["The confirm password field is required."]},"status_code":422}}
```

Does anybody know what would be causing this issue? Any help is greatly appreciated.