Batch reading for Externally stored resource during search

[volodymyr-korzh]

When FHIR Resource Body is stored outside the FHIR database HFJ_RES_VER.RES_ENCODING = ESR (Externally stored resource), search operation takes significantly more time comparing to when resource bodies are store in Database.

To Reproduce

1. Create 50 Patient resources with resource bodies stored outside of HFJ_RES_VER tabled (HFJ_RES_VER.RES_ENCODING = ESR)
2. Execute GET http://localhost:8000/Patient

Actual behaviour

Response returned in [time to read external resource]*50 e. g. 100ms*50 = 5000ms (5 seconds)

Expected behaviour
Response returned in ~[time to read external resource] e. g. ~100ms