Helper Methods for Validators

## Helper Methods for Validators

### Acceptance Criteria
1. `createNonEmptyConstraintViolationList` exists in `ControllerTestCase` and returns a ConstraintViolationList with ConstraintViolation mocks.
1. `createConstraintViolationResponse` exists in `AbstractController`. It takes a ConstraintViolationList and returns a JsonResponse with this format: `['errors' => $errors]` where `$errors` is the output of the ConstraintViolationList's getArrayCopy method.

### Tasks
- None

### Additional Notes
- `createNonEmptyConstraintViolationList` will be used to test controllers that use validators.