Service-info updates

[jsstevenson]

Feature description

• Use jsonschema for unit test
• Try to get last updated timestamp

Use case

Simplifies testing

Acceptance Criteria

• Use jsonschema for unit test (see anyvar PR)
• Get last updated timestamp in code? Not sure

Proposed solution

No response

Alternatives considered

No response

Implementation details

No response

Potential Impact

No response

Additional context

No response

Contribution

Yes, I can create a PR for this feature.

[jsstevenson]

The current jsonschema checks rely on a deprecated method, trying to figure out referencing

• https://referencing.readthedocs.io/en/stable/
• How to build a registry from a simple OpenAPI document dict? python-jsonschema/referencing#160