Problem Description: 

Setting the key `COLLECTION_SIGNING_SERVICE="unique-name"` on `/etc/pulp/settings.py` or as equivalent environment variable.
```bash

1. setting.py
   COLLECTION_SIGNING_SERVICE="ansible-default"
   COLLECTION_SIGNING_ON_APPROVAL=True
   ```

will set that signing service to the whole system

QA Criteria: 

• The configured signing service is the one use on automatic approvals post sign

Affects: Backend, Settings, Installer