feat(retrieval): add Perplexity attribution header (#24833)

Signed-off-by: James Liounis <james.liounis@perplexity.ai>

backend/open_webui/retrieval/web/perplexity_search.py

@@ -2,6 +2,7 @@ import logging
 from typing import Literal, Optional
 
 import requests
+from open_webui.env import VERSION
 from open_webui.retrieval.web.main import SearchResult, get_filtered_results
 from open_webui.utils.headers import include_user_info_headers
 
@@ -47,6 +48,7 @@ def search_perplexity_search(
         headers = {
             'Authorization': f'Bearer {api_key}',
             'Content-Type': 'application/json',
+            'X-Pplx-Integration': f'open-webui/{VERSION}',
         }
 
         # Forward user info headers if user is provided