Raise an exception for unknown CSPs

[jesusbv]

Description

Instead of saving nil or empty value on the DB for system_token field, raise an exception if the CSP value from the metadata is unknown

How to test

Create a system with an unknown CSP, request should fail

Change Type

Please select the correct option.

• [ ] Bug Fix (a non-breaking change which fixes an issue)
• [X] New Feature (a non-breaking change which adds new functionality)
• [ ] Documentation Update (a change which only updates documentation)

Checklist

Please check off each item if the requirement is met.

• [X] I have reviewed my own code and believe that it's ready for an external review.
• [X] I have provided comments for any hard-to-understand code.
• [ ] I have documented the MANUAL.md file with any changes to the user experience.
• [ ] If my changes are non-trivial, I have added a changelog entry to notify users at package/obs/rmt-server.changes.

Review

Please check out our review guidelines and get in touch with the author to get a shared understanding of the change.