Redis langserve template (#12443)

Add Redis langserve template! Eventually will add semantic caching to
this too. But I was struggling to get that to work for some reason with
the LCEL implementation here.

- **Description:** Introduces the Redis LangServe template. A simple RAG
based app built on top of Redis that allows you to chat with company's
public financial data (Edgar 10k filings)
  - **Issue:** None
- **Dependencies:** The template contains the poetry project
requirements to run this template
  - **Tag maintainer:** @baskaryan @Spartee 
  - **Twitter handle:** @tchutch94

**Note**: this requires the commit here that deletes the
`_aget_relevant_documents()` method from the Redis retriever class that
wasn't implemented. That was breaking the langserve app.

---------

Co-authored-by: Sam Partee <sam.partee@redis.com>

libs/langchain/langchain/vectorstores/redis/base.py

@@ -24,10 +24,7 @@ import numpy as np
 import yaml
 
 from langchain._api import deprecated
-from langchain.callbacks.manager import (
-    AsyncCallbackManagerForRetrieverRun,
-    CallbackManagerForRetrieverRun,
-)
+from langchain.callbacks.manager import CallbackManagerForRetrieverRun
 from langchain.docstore.document import Document
 from langchain.schema.embeddings import Embeddings
 from langchain.schema.vectorstore import VectorStore, VectorStoreRetriever
@@ -1450,11 +1447,6 @@ class RedisVectorStoreRetriever(VectorStoreRetriever):
             raise ValueError(f"search_type of {self.search_type} not allowed.")
         return docs
 
-    async def _aget_relevant_documents(
-        self, query: str, *, run_manager: AsyncCallbackManagerForRetrieverRun
-    ) -> List[Document]:
-        raise NotImplementedError("RedisVectorStoreRetriever does not support async")
-
     def add_documents(self, documents: List[Document], **kwargs: Any) -> List[str]:
         """Add documents to vectorstore."""
         return self.vectorstore.add_documents(documents, **kwargs)