In case we send a request to Personalization restfrontend for non existing mandator (example: https://admin.test.perso.ibexa.co/api/v3/-1/structure/get_model/top_clicked) in response we receive fault code modelNotFoundFault. Instead we should receive fault code mandatorNotFound.

Steps to reproduce:
1. Send a request to https://admin.test.perso.ibexa.co/api/v3/-1/structure/get_model_/<any_model_ref_code> with admin authorization. Edit: update_model endpoint also has the same issue.

Expected result:
1. Since mandator does not exists we should receive fault code containing that information

Actual result:
1. Response contains fault code: modelNotFoundFault

DoD:
After bug has been fixed please update e2e tests repository . All of the places which need to be updated are marked with @Bug("IBX-xxxx") annotation.