The SageMaker embedding handler was not using _load_credentials(),
which meant aws_role_name and aws_session_name parameters were
ignored. This prevented cross-account role assumption for embeddings
while it worked for completions.
Changes:
- Replace direct boto3 client creation with _load_credentials() call
- Create boto3.Session with assumed credentials
- Add comprehensive unit tests for role assumption
This aligns the embedding handler behavior with the completion handler,
which already supports role assumption via the BaseAWSLLM.get_credentials()
method.
Fixes cross-account SageMaker embedding access where users need to
assume a role in another account to invoke endpoints.
33d4b93bee