[server] - Add Webhook Retry Logic and Dead-Letter Queue

[dark-sarge]

Location: server/src/routes/webhooks.ts, server/src/jobs/processors/

Description

Paystack may re-deliver webhooks if the server does not respond in time. Currently there is no idempotency layer beyond the Paystack reference check. Additionally, failed webhook processing (e.g. due to a temporary database outage) has no retry mechanism, meaning events could be permanently lost.

Acceptance Criteria

• A webhook_events table is created with columns: id, provider (paystack), event_type, payload (JSONB), processed_at, status (pending, processed, failed).
• On receipt of a valid Paystack webhook, the raw payload is immediately persisted to webhook_events with status: pending before any processing begins.
• A BullMQ job is enqueued to process the event asynchronously; the HTTP response returns 200 immediately.
• If the job processor fails, BullMQ retries up to 3 times with exponential backoff. After 3 failures the event is marked failed and an admin alert is sent.
• A GET /api/admin/webhooks (admin only) endpoint lists failed webhook events with their payloads for manual inspection and replay.
• A POST /api/admin/webhooks/:id/replay (admin only) re-enqueues a failed webhook event for reprocessing.

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[temieehade-coder]

@temieehade-coder has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer, i can fix this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @temieehade-coder to this issue.

[theophilus2530]

@theophilus2530 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer, I’ve reviewed the issue and understand what’s required. I’m confident I can deliver a clean solution that meets the criteria. I’d appreciate the opportunity to take it on.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @theophilus2530 to this issue.

[EbukaMoses]

@EbukaMoses has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello Maintainer,

I’d like to apply to work on this issue.

I’m Ebuka Moses, a full-stack and blockchain developer with experience building, testing, and maintaining smart contracts, particularly using Rust and blockchain-based architectures. I’m comfortable working with contract logic, validation, access control, persistent storage, and event handling, and I always pay close attention to correctness, security, and edge cases.

I take time to fully understand the issue requirements before implementing a solution, and I ensure my work follows the project’s coding standards. I also write clear, well-tested code and submit clean pull requests with meaningful commits.

I’m confident I can deliver a solid solution that meets the acceptance criteria and adds value to the project.

Thank you for your consideration, and I look forward to contributing.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @EbukaMoses to this issue.