🧹 [Maintenance]: Update RFC Draft for Idempotency Middleware

[gaby]

Maintenance Task Description

The draft RFC for the idempotency middleware links to a draft documentation that expired 1 year ago. We should compare the one linked in the documentation with the latest draft and update the middleware accordingly.

Draft in Docs: https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-idempotency-key-header-02
Latest Draft: https://datatracker.ietf.org/doc/html/draft-ietf-httpapi-idempotency-key-header-04

Impact on the Project

No response

Additional Context (optional)

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Checklist:

• I have confirmed that this maintenance task is currently not being addressed.
• I understand that this task will be evaluated by the maintainers and prioritized accordingly.
• I am available to provide further information if needed.

[gaby]

Note: I noticed this while updating/cleaning the README.md in a local branch.