Vectara - minor update (#7954)

CONTRIBUTING.md

@@ -99,6 +99,17 @@ See [Storage guide](https://gpt-index.readthedocs.io/en/latest/how_to/storage.ht
 
 ---
 
+#### Managed Index
+
+A managed index is used to represent an index that's managed via an API, exposing API calls to index documents and query documents.
+
+Currently we support the [VectaraIndex](https://github.com/run-llama/llama_index/tree/ca09272af000307762d301c99da46ddc70d3bfd2/llama_index/indices/managed/vectara). 
+Open to contributions!
+
+See [Managed Index docs](https://gpt-index.readthedocs.io/en/stable/community/integrations/managed_indices.html) for details.
+
+---
+
 #### Vector Stores
 
 Our vector store classes store embeddings and support lookup via similarity search.

docs/community/integrations/managed_indices.md

@@ -14,8 +14,8 @@ Below we show how to use it.
 
 **Vectara Index Construction/Querying**
 
-Use the [Vectara Console](https://console.vectara.com/login) to create a corpus (aka Index), and add an API key for access. 
-Then put the customer id, corpus id, and API key in your environment as shown below.
+First, [sign up](https://vectara.com/integrations/llama_index) and use the Vectara Console to create a corpus (aka Index), and add an API key for access. 
+Then put the customer id, corpus id, and API key in your environment.
 
 Then construct the Vectara Index and query it as follows:
 

llama_index/indices/managed/vectara/base.py

@@ -113,6 +113,7 @@ class VectaraIndex(BaseManagedIndex):
             "x-api-key": self._vectara_api_key,
             "customer-id": self._vectara_customer_id,
             "Content-Type": "application/json",
+            "X-Source": "llama_index",
         }
 
     def _delete_doc(self, doc_id: str) -> bool:

llama_index/indices/managed/vectara/retriever.py

@@ -57,6 +57,7 @@ class VectaraRetriever(BaseRetriever):
             "x-api-key": self._index._vectara_api_key,
             "customer-id": self._index._vectara_customer_id,
             "Content-Type": "application/json",
+            "X-Source": "llama_index",
         }
 
     def _retrieve(