fix: add botocore credentials extraction and conversion

The code changes in `bedrock_httpx.py` add functionality to extract and convert AWS STS credentials to session credentials using botocore. This fixes later error in add_auth request when token needs to be assigned.

litellm/llms/bedrock_httpx.py

@@ -45,6 +45,7 @@ import httpx  # type: ignore
 from .bedrock import BedrockError, convert_messages_to_prompt, ModelResponseIterator
 from litellm.types.llms.bedrock import *
 import urllib.parse
+import botocore
 
 
 class AmazonCohereChatConfig:
@@ -261,7 +262,14 @@ class BedrockLLM(BaseLLM):
                 RoleArn=aws_role_name, RoleSessionName=aws_session_name
             )
 
-            return sts_response["Credentials"]
+            # Extract the credentials from the response and convert to Session Credentials
+            sts_credentials = sts_response["Credentials"]
+            credentials = botocore.credentials.Credentials(
+                access_key=sts_credentials["AccessKeyId"],
+                secret_key=sts_credentials["SecretAccessKey"],
+                token=sts_credentials["SessionToken"],
+            )
+            return credentials
         elif aws_profile_name is not None:  ### CHECK SESSION ###
             # uses auth values from AWS profile usually stored in ~/.aws/credentials
             client = boto3.Session(profile_name=aws_profile_name)