partner[minor]: Astra DB clients identify themselves as coming through LangChain package (#18131)

**Description**

This PR sets the "caller identity" of the Astra DB clients used by the
integration plugins (`AstraDBChatMessageHistory`, `AstraDBStore`,
`AstraDBByteStore` and, pending #17767 , `AstraDBVectorStore`). In this
way, the requests to the Astra DB Data API coming from within LangChain
are identified as such (the purpose is anonymous usage stats to best
improve the Astra DB service).

libs/partners/astradb/langchain_astradb/utils/astradb.py

@@ -6,6 +6,7 @@ from asyncio import InvalidStateError, Task
 from enum import Enum
 from typing import Awaitable, Optional, Union
 
+import langchain_core
 from astrapy.db import AstraDB, AsyncAstraDB
 
 
@@ -51,13 +52,13 @@ class _AstraDBEnvironment:
             )
 
         if astra_db:
-            self.astra_db = astra_db
+            self.astra_db = astra_db.copy()
             if async_astra_db:
-                self.async_astra_db = async_astra_db
+                self.async_astra_db = async_astra_db.copy()
             else:
                 self.async_astra_db = self.astra_db.to_async()
         elif async_astra_db:
-            self.async_astra_db = async_astra_db
+            self.async_astra_db = async_astra_db.copy()
             self.astra_db = self.async_astra_db.to_sync()
         else:
             raise ValueError(
@@ -65,6 +66,15 @@ class _AstraDBEnvironment:
                 "'token' and 'api_endpoint'"
             )
 
+        self.astra_db.set_caller(
+            caller_name="langchain",
+            caller_version=getattr(langchain_core, "__version__", None),
+        )
+        self.async_astra_db.set_caller(
+            caller_name="langchain",
+            caller_version=getattr(langchain_core, "__version__", None),
+        )
+
 
 class _AstraDBCollectionEnvironment(_AstraDBEnvironment):
     def __init__(