InternalHttpException Thrown with Validation on Internal Requests in 2.0.0-alpha2

| Q | A
| ----------------- | ---
| Bug? | yes
| New Feature? | no
| Framework | Laravel
| Framework version | 5.6.*
| Package version | 2.0.0-alpha2
| PHP version | 7.2.1

#### Actual Behaviour

Given the following controller method:

```
public function store(Request $request, $location_id)
{
$validator = Validator::make($request->all(), [
'name' => 'required|max:191',
]);

if ($validator->fails()) {
throw new StoreResourceFailedException('Could not create contact record.', $validator->errors());
}

// Continue with the rest of this method...
}
```
The method will work just fine if consuming the API by itself, but for _internal requests_, it will always throw an `InternalHttpException` for failed validation instead of `StoreResourceFailedException`.

#### Expected Behaviour

We should be able to specify the exception to be thrown, but it currently only throws `InternalHttpException` for internal requests.

#### Steps to Reproduce

Copy and paste the method above into a controller and try to make an internal request to it.

#### Possible Solutions

This feature seemed to work fine in version `2.0.0-alpha1`, but no longer works in `2.0.0-alpha2`. So maybe revert something back to the way it used to be...