Migrate API upload from create_or_update_arc to create_harvest/submit_arc_in_harvest

[Zalfsten]

Background

The converter currently calls ApiClient.create_or_update_arc(rdi, arc) in processor.py to upload each ARC to the FAIRagro Middleware API.

This method is outdated. The API now uses a harvest-based workflow.

Required Change

Replace the single create_or_update_arc call with the two-step harvest API:

1. ApiClient.create_harvest(rdi) — create a harvest session for the RDI
2. ApiClient.submit_arc_in_harvest(harvest_id, arc) — submit each ARC within that harvest

The exact interface of these methods needs to be verified against the current middleware.api_client library.

Files to change

• middleware/sql_to_arc/src/middleware/sql_to_arc/processor.py — replace the upload call
• .specifica/features/api-upload/spec.md — update requirements to reflect the new API contract

Acceptance Criteria

• create_or_update_arc is no longer called anywhere in sql_to_arc
• The harvest workflow is covered by integration tests
• .specifica/features/api-upload/spec.md describes the new contract