TODO

Core client and JetStream capabilities

• [ ] Add JWT-based authorization, including a JWT callback and nonce-signing callback for user credentials.
• [ ] Surface No Responders (503) responses from request/reply operations as a distinct result.
• [ ] Handle Lame Duck Mode server notifications by draining or reconnecting before the server closes the client connection.
• [ ] Add client-side draining for subscriptions and pending publishes.
• [ ] Add JetStream Key-Value Store APIs.
• [ ] Add JetStream Object Store APIs.