As soon as OAI-PMH view in Inventory is divided into two as per
MODINVSTOR-536, data retrieval should be changed in the next way:
- First call should query the view, which makes required filtering and returns all result instances UUIDs.
- These UUIDs are stored in OAI-PMH internal database
- All sequential requests should go to the second view, which returns holdings and items data, according to flow control principles.