Align Geofencing with guidelines for error scenarios

[maxl2287]

Problem description Current version still does not follow the recent guidelines.

Possible evolution Align codes and examples as indicated in:

https://github.com/camaraproject/Commonalities/blob/main/artifacts/camara-cloudevents/event-subscription-template.yaml

Additional context Related issues for:

• Location retrieval #219
• Location verification #214