Add template for self-query-qdrant (#12795)

This PR adds a self-querying template using Qdrant as a vector store.
The template uses an artificial dataset and was implemented in a way
that simplifies passing different components and choosing LLM and
embedding providers.

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

templates/self-query-qdrant/self_query_qdrant/helper.py

@@ -0,0 +1,27 @@
+from string import Formatter
+from typing import List
+
+from langchain.schema import Document
+
+document_template = """
+PASSAGE: {page_content}
+METADATA: {metadata}
+"""
+
+
+def combine_documents(documents: List[Document]) -> str:
+    """
+    Combine a list of documents into a single string that might be passed further down
+    to a language model.
+    :param documents: list of documents to combine
+    :return:
+    """
+    formatter = Formatter()
+    return "\n\n".join(
+        formatter.format(
+            document_template,
+            page_content=document.page_content,
+            metadata=document.metadata,
+        )
+        for document in documents
+    )