Add system token for PAYG systems

[jesusbv]

Description

Add system-token to PAYG systems

How to test

Create a PAYG system, in the RMT the system token value should be the instance ID

Change Type

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• [ ] 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

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