Do NOT fetch invalid items by default - BHS-133
Do NOT fetch invalid items by default - BHS-133

- Simplified the flow of _fetch_item
- Moved the call to enrich_item to batch_related script
- Added doctest to _fetch_item()
- Simplified fetch_items()
- Added debug mode to /item/ API endpoint

Beit-Hatfutsot/dbs-back,Beit-Hatfutsot/dbs-back,Beit-Hatfutsot/dbs-back,Beit-Hatfutsot/dbs-back