community[patch]: update apify integration to attribute API activity to langchain (#21909)

**Description:** Add `Origin/langchain` to Apify's client's user-agent
to attribute API activity to LangChain (at Apify, we aim to monitor our
integrations to evaluate whether we should invest more in the LangChain
integration regarding functionality and content)

**Issue:** None
**Dependencies:** None
**Twitter handle:** None

libs/community/langchain_community/document_loaders/apify_dataset.py

@@ -60,7 +60,11 @@ class ApifyDatasetLoader(BaseLoader, BaseModel):
         try:
             from apify_client import ApifyClient
 
-            values["apify_client"] = ApifyClient()
+            client = ApifyClient()
+            if httpx_client := getattr(client.http_client, "httpx_client"):
+                httpx_client.headers["user-agent"] += "; Origin/langchain"
+
+            values["apify_client"] = client
         except ImportError:
             raise ImportError(
                 "Could not import apify-client Python package. "