Add configurable Google Drive toggle in the Documents admin section along with necessary config scaffolding

backend/open_webui/config.py

@@ -1438,6 +1438,13 @@ RAG_WEB_SEARCH_DOMAIN_FILTER_LIST = PersistentConfig(
     ],
 )
 
+# If configured, Google Drive will be available as an upload option.
+ENABLE_GOOGLE_DRIVE = PersistentConfig(
+    "ENABLE_GOOGLE_DRIVE",
+    "rag.drive.enable",
+    os.getenv("ENABLE_GOOGLE_DRIVE", "False").lower() == "true",
+)
+
 SEARXNG_QUERY_URL = PersistentConfig(
     "SEARXNG_QUERY_URL",
     "rag.web.search.searxng_query_url",