Update createNotFoundResponse to return same response as a missing route

## Update createNotFoundResponse to return same response as a missing route

### Acceptance Criteria
1. `AbstractController::createNotFoundResponse` returns a 404 with the following body:
```JSON
{
    "messages" : "Not found"
}
```

### Tasks
- Modify AbstractController::createNotFoundResponse to return `JsonResponse` rather than `Response`.

### Additional Notes
- Related to #133