v0.2.7 — split ServiceStatus sidecar out of upload payload

Split the service.json status sidecar out of the upload payload.

The seller_api upload body now carries authored content and the backend identity record as two separate fields:

• data — ServiceDataInput: provider / offering / listing content
• service_status — ServiceStatus: the service.json identity record (service_id, revision_of, status, template_instance_id, …), sent only when one exists

Matches the backend rework in unitysvc#1291 and the ServiceData → ServiceStatus rename in unitysvc-core 0.2.3. Requires unitysvc-core>=0.2.3.

PR: unitysvc/unitysvc-sellers#101