Indexer: add outbound webhook delivery guarantees

[Otaiki1]

Build location

Work primarily in indexer/src/webhooks. Keep related tests/docs beside that package unless this issue explicitly calls for a cross-package update.

Why this matters

Indexer webhooks should retry, sign payloads, track delivery status, and avoid duplicate downstream notifications.

What to build

• Review webhook.service and webhook entity.
• Add delivery state machine and retry schedule.
• Sign outbound payloads and include event IDs.

Acceptance criteria

• Tests cover successful delivery, retry, permanent failure, and duplicate suppression.
• Webhook consumers receive idempotency keys.

Suggested verification

cd indexer && npm run lint && npm run test && npm run build

[code-0-stella]

@code-0-stella has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hey, I would like to be assigned to this issue. I will enhance the indexer webhook delivery system by implementing a delivery state machine, retry scheduling with failure handling, signed outbound payloads with event IDs and idempotency keys, and comprehensive tests covering successful delivery, retries, permanent failures, and duplicate suppression.

Can I be assigned to this issue?

ℹ️ Repo Maintainers: To accept this application, review their application or assign @code-0-stella to this issue.

[Zarmaijemimah]

@Zarmaijemimah has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I’ll love to work on this issue please kindly assign thank you.

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

[drips-wave]

Congratulations, @Zarmaijemimah! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @Zarmaijemimah: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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