Update elasticsearch_backend.py, added support 'track_total_hits'

Support track_total_hits Handling in ElasticsearchSearchBackend

- Implemented handling for `track_total_hits` in the Elasticsearch search backend.
- Supports `bool` values (True/False) and `int` values.
- Added a warning for invalid `track_total_hits` values.
- Ensured the parameter is only added to search kwargs when valid.

haystack/backends/elasticsearch_backend.py

@@ -15,6 +15,7 @@
     FUZZY_MAX_EXPANSIONS,
     FUZZY_MIN_SIM,
     ID,
+    TRACK_TOTAL_HITS,
 )
 from haystack.exceptions import MissingDependency, MoreLikeThisError, SkipDocument
 from haystack.inputs import Clean, Exact, PythonData, Raw
@@ -545,6 +546,28 @@ def build_search_kwargs(
         if extra_kwargs:
             kwargs.update(extra_kwargs)
 
+        # If TRACK_TOTAL_HITS is False, 0, or None, do not include the parameter
+        if TRACK_TOTAL_HITS:
+            # Define a mapping for the track_total_hits parameter
+            # - If TRACK_TOTAL_HITS is True (bool), map to "true" (string)
+            # - If TRACK_TOTAL_HITS is an integer, use its value directly
+            track_total_hits_mapper = {
+                bool: "true",  # Maps boolean True to "true"
+                int: TRACK_TOTAL_HITS,  # Maps integer to its value
+            }
+
+            # Get the mapped value based on the type of TRACK_TOTAL_HITS
+            # If the type is not in the mapper, fallback to False
+            track_total_hits = track_total_hits_mapper.get(type(TRACK_TOTAL_HITS), False)
+
+            # If a valid track_total_hits value is obtained, add it to search_kwargs
+            if track_total_hits:
+                search_kwargs['track_total_hits'] = track_total_hits
+            else:
+                # Issue a warning if TRACK_TOTAL_HITS is not of type bool or int
+                warnings.warn(
+                    "Wrong value of HAYSTACK_TRACK_TOTAL_HITS is provided. Valid options are `bool` or `int`."
+                )
         return kwargs
 
     @log_query