Align subscription-APIs 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

[akoshunyadi]

We've aligned with the event-subscription-template.yaml, shouldn't that be first aligned with the guideline? @bigludo7

[bigludo7]

We've aligned with the event-subscription-template.yaml, shouldn't that be first aligned with the guideline? @bigludo7

Yes! we need to align our template yaml with the commonalities.
@maxl2287 have you already done the gap list?