feat(component): feat(webhook): Adds support for interactive nfm_reply payloads (WhatsApp Flows) in the webhook parser and improves signature hashing

[RyzorBent]

Description of change

Adds support for interactive nfm_reply payloads (WhatsApp Flows) in the webhook parser and improves signature hashing by normalizing the request buffer before computing the HMAC. This keeps interactive replies consistent across types and avoids signature verification issues in environments where the raw body is a Buffer-like object.

Verification:

• Not run locally (not requested)

Pull-Request Checklist

• Code is up-to-date with the main branch
• npm run lint passes with this change
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000 (N/A)
• There are new or updated unit tests validating the change (N/A)
• Documentation has been updated to reflect this change (N/A)
• The new commits follow conventions outlined in the https://www.conventionalcommits.org/en/v1.0.0/

[gemini-code-assist]

Summary of Changes

Hello @RyzorBent, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request integrates support for WhatsApp Flows' interactive nfm_reply messages into the webhook parser, allowing the system to properly interpret and process these new types of interactive responses. Concurrently, it refines the webhook signature hashing mechanism to ensure robustness and prevent verification failures that could arise from inconsistencies in request body handling across various Node.js environments.

Highlights

• WhatsApp Flows (nfm_reply) Support: The webhook parser now correctly handles interactive nfm_reply payloads, which are part of WhatsApp Flows, allowing the system to process these new interactive responses.
• Enhanced Signature Hashing: The webhook signature verification process has been improved by normalizing the request body to a Uint8Array before HMAC computation, ensuring consistent and reliable signature validation across different environments.

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[gemini-code-assist]

Code Review

This pull request introduces support for interactive nfm_reply payloads from WhatsApp Flows and enhances the security of webhook signature verification. While the signature hashing is made more robust by normalizing the request buffer, the signature verification logic remains vulnerable to a timing attack due to the use of a standard string comparison for the HMAC hash. It is recommended to remediate this by using a constant-time comparison function like crypto.timingSafeEqual. Additionally, a small refactoring in the webhook handler could simplify the logic for processing interactive messages, improving code clarity and maintainability.

[RyzorBent]

This PR addresses -> #4