Added CosmosDB warning: Use CosmosDbPartitionedStorage instead. (#2104)

* Added CosmosDB warning * CosmosDBStorage black --------- Co-authored-by: Tracy Boehrer <trboehre@microsoft.com>

Author: tracyboehrer

libraries/botbuilder-azure/botbuilder/azure/cosmosdb_storage.py

@@ -7,6 +7,7 @@
 from typing import Dict, List
 from threading import Semaphore
 import json
+import warnings
 from jsonpickle.pickler import Pickler
 from jsonpickle.unpickler import Unpickler
 import azure.cosmos.cosmos_client as cosmos_client # pylint: disable=no-name-in-module,import-error
@@ -107,6 +108,9 @@ def __init__(
  :param config:
  """
  super(CosmosDbStorage, self).__init__()
+ warnings.warn(
+ "CosmosDbStorage is obsolete. Use CosmosDbPartitionedStorage instead."
+ )
  self.config = config
  self.client = client or cosmos_client.CosmosClient(
  self.config.endpoint, {"masterKey": self.config.masterkey}