✨(backend) use batches in indexing task

Reduce the number of Find API calls by grouping all the latest changes
for indexation : send all the documents updated or deleted since the
triggering of the task.

Signed-off-by: Fabre Florian <ffabre@hybird.org>

src/backend/core/tests/conftest.py

@@ -45,6 +45,7 @@ def indexer_settings_fixture(settings):
     settings.SEARCH_INDEXER_QUERY_URL = (
         "http://localhost:8081/api/v1.0/documents/search/"
     )
+    settings.SEARCH_INDEXER_COUNTDOWN = 1
 
     yield settings