feat(checkpoint-bedrock): Add bedrock checkpointer

[cwoolum]

Overview

This PR introduces a new package @langchain/langgraph-checkpoint-bedrock that implements a CheckpointSaver for LangGraph.js using Amazon Bedrock Agent Runtime sessions for persistence. This implementation allows LangGraph applications to securely store and retrieve conversation state and context across multi-step generative AI workflows without requiring custom backend solutions.

Features

• Implements BedrockSessionSaver class that extends BaseCheckpointSaver from LangGraph
• Provides seamless integration with Amazon Bedrock Agent Runtime sessions API
• Supports storing and retrieving checkpoint data with proper serialization
• Handles pending writes and task sends for complex workflow states
• Implements checkpoint listing with filtering capabilities
• Supports session creation with optional customer-managed KMS keys for enhanced security
• Provides flexible AWS credential configuration options

Implementation Details

• Uses Amazon Bedrock Agent Runtime sessions to store LangGraph checkpoints
• Implements the full CheckpointSaver interface including put, getTuple, putWrites, and list methods
• Organizes checkpoint data using invocations and invocation steps in Bedrock sessions
• Handles serialization/deserialization of complex checkpoint data structures
• Implements proper error handling for AWS service exceptions
• Provides utility functions for AWS configuration and checkpoint management

Security Considerations

• Supports AWS IAM for access control to session data
• Implements optional customer-managed KMS key encryption
• Follows AWS best practices for credential management

Testing

• Includes unit tests for utility functions
• Provides integration tests for the full checkpoint lifecycle

Documentation

• Comprehensive README with installation and usage instructions
• Code examples for common use cases
• Detailed JSDoc comments for all public APIs

Dependencies

• Requires @aws-sdk/client-bedrock-agent-runtime as a peer dependency

[cwoolum]

@vbarda, are you taking PR's to this repo right now?