Add support for NATS JetStream as a transport

[joeriddles]

closes #2103

Implement support for NATS using its built-in persistence layer JetStream.

Example

You can test using either:

• Installing the NATS server locally and running it with JetStream enabled: nats-server --js
• Using the demo NATS server at demo.nats.io

The transport can be test using examples/nats_receive.py and examples/nats_send.py:

1. Start the local NATS server (optional)
2. Run python -m examples.nats_receive (append --demo if using the demo server)
3. In another window, run python -m examples.nats_send (append --demo if using the demo server)

In the receive window, you should see something like:

Received message: 'hello world'
  properties:
{   'body_encoding': 'base64',
    'delivery_info': {'exchange': 'exchange', 'routing_key': 'messages'},
    'delivery_mode': 2,
    'delivery_tag': 'fa01f1a9-f666-46a0-af71-35e5164e1ad9',
    'priority': 0}
  delivery_info:
{'exchange': 'exchange', 'routing_key': 'messages'}

[Copilot]

Pull Request Overview

Adds initial support for NATS JetStream as a Kombu transport, including dependency, transport registration, and usage examples.

• Adds nats-py extra requirement
• Registers the nats transport in Kombu’s transport registry
• Provides example scripts for sending and receiving messages via NATS JetStream

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

File	Description
requirements/extras/nats.txt	Pins the nats-py[nkeys] dependency
kombu/transport/init.py	Registers 'nats' transport for JetStream
examples/nats_send.py	Example for publishing messages to JetStream
examples/nats_receive.py	Example for consuming messages from JetStream

Comments suppressed due to low confidence (1)

kombu/transport/init.py:48

• [nitpick] The transport key 'nats' is generic and could conflict with other NATS-based transports; consider renaming it to 'nats_jetstream' to clearly distinguish this implementation.

'nats': 'kombu.transport.nats_jetstream:Transport',

[Nusnus]

Please ping me when the PR is ready for review. Thank you for working on this!

[joeriddles]

Please ping me when the PR is ready for review. Thank you for working on this!

@Nusnus ready for review!

[joeriddles]

@Nusnus @auvipy I fixed the merge conflicts and rebased on main

[auvipy]

tried to fix the merge conflicts, but feel free to improve it

[joeriddles]

Thanks @auvipy, I fixed tox.ini but otherwise the merge looks good

[maxyloon]

Just wanted to spread the love. So looking forward for this integration!