API 2.9: Making id attribute of revocation object required

[JuAlMan]

Using image docker.sunet.se/dc4eu/apigw:apiv28

Currently all attributes in revocation object are optional.

We propose that the id attribute should be required as using an empty revocation object doen not make much sense.
Especially when using the /document/revoke call it seems to be necessary to submit a revocation id.
When uploading, one could leave out the revocation object as a whole if submitting a revocation_id that is different from the document_id is not required.

We also changed this in the API v29 spec.