Description of problem:
When the "configuration_script" attribute is requested the request fails with internal server error:

{
    "error": {
        "kind": "internal_server_error",
        "message": "Association named 'configuration_script' was not found on Service; perhaps you misspelled it?",
        "klass": "ActiveRecord::AssociationNotFoundError"
    }
}

However the attribute is listed under the "relationships", so it should be possible to requested in the same way as all the other attributes.
See
OPTIONS /api/services


Version-Release number of selected component (if applicable):
5.9.0.18


How reproducible:
100%


Steps to Reproduce:
1. create service, e.g.
POST /api/services
{ "name": "myservice01" }
2. request the "configuration_script" attribute
GET /api/services?expand=resources&attributes=configuration_script