feat(transport): add valkey and valkeys

[Zerotask]

This PR adds the alternative transport schemes valkey and valkeys, which is also the recommendation from django-valkey.

Fixes #2245

I didn't update the documentation because I first want to get feedback.
There could be a new page for Valkey or just an addition for the Redis transport here:
https://docs.celeryq.dev/projects/kombu/en/stable/reference/kombu.transport.redis.html

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Valkey is an open source drop-in replacement for Redis:

This project was forked from the open source Redis project right before the transition to their new source available licenses.
(https://github.com/valkey-io/valkey)

https://django-valkey.readthedocs.io/en/latest/configure/advanced_configurations.html

[Nusnus]

See celery/celery#9300

[Zerotask]

See celery/celery#9300

Thank you for referencing that. So this is a blocker and it probably needs a new Valkey transport implementation in kombu?

We recently switched from Redis to Valkey and didn't experience any issues with celery. It works as before.

[Nusnus]

See celery/celery#9300

Thank you for referencing that. So this is a blocker and it probably needs a new Valkey transport implementation in kombu?

We recently switched from Redis to Valkey and didn't experience any issues with celery. It works as before.

I don't recall all of the details, but the other issue explains where we are right now.

[auvipy]

I think we might be able to use same code for two differently named backend named redis / valkey / dragonfly etc

[auvipy]

Yes, this makes most sense as we do not need to maintain double code for the same back end

[auvipy]

just adding docs and may be should be OK for now

[flipsed]

any updates on this @Zerotask ?

[Zerotask]

just adding docs and may be should be OK for now

Since there might be a standalone backend in the future, I just added very basic docs, so people will know about this.
Is this okay or is there anything specific missing? @auvipy @Nusnus

[Copilot]

Pull Request Overview

This PR adds support for Valkey transport schemes (valkey and valkeys) as alternative connection protocols to the existing Redis transport, since Valkey is an open-source drop-in replacement for Redis.

• Adds Valkey transport scheme mappings to use the existing Redis transport implementation
• Updates documentation to include Valkey connection examples and transport comparison entries
• Adds Valkey references to README keywords and features sections

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
kombu/transport/init.py	Maps valkey/valkeys schemes to Redis transport
kombu/transport/redis.py	Adds Valkey connection string documentation
docs/userguide/connections.rst	Adds Valkey URL example and transport comparison entry
README.rst	Updates keywords and features to mention Valkey support

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