Add validation on 'skippedStatus' property

When lauching the service, the value of property 'skippedStatus' is not well managed.

• if value is 'error', then its value is 'error'
• if any non-null value is given, then value becomes 'success'
• if no value is given, then its value becomes 'error'

Expected:

We need to change de second point and add an error message if a non-null value different from 'error' or 'success' is given.