feat(webhooks): add the account deletion reason into webhooks

[chenba]

Because:

• RPs might want to handle account deletions differently based on the reason

This commit:

• maps the deletion reasons to a set of public reasons
• includes the reason in SQS events
• adds the reason to the delete-user webhook event

[Copilot]

🟡 Changes recommended

The public reason contract is duplicated across packages and can drift, causing valid future reasons to be silently discarded.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds public account-deletion reasons to SQS notifications and delete-user webhook events while preserving legacy events.

Changes:

• Maps internal deletion reasons to public values.
• Validates and propagates reasons through the event broker.
• Adds coverage for mapped, missing, and invalid reasons.

File summaries

File	Description
packages/fxa-event-broker/src/queueworker/sqs.dto.ts	Adds the optional incoming reason.
packages/fxa-event-broker/src/queueworker/queueworker.service.ts	Validates and fans out reasons.
packages/fxa-event-broker/src/queueworker/queueworker.service.spec.ts	Tests reason fan-out and fallbacks.
packages/fxa-event-broker/src/pubsub-proxy/pubsub-proxy.controller.ts	Passes valid reasons to SET generation.
packages/fxa-event-broker/src/pubsub-proxy/pubsub-proxy.controller.spec.ts	Tests valid and invalid reasons.
packages/fxa-event-broker/src/jwtset/set.interface.ts	Extends delete-event input.
packages/fxa-event-broker/src/jwtset/jwtset.service.ts	Adds reasons to delete SETs.
packages/fxa-event-broker/src/jwtset/jwtset.service.spec.ts	Tests generated SET payloads.
packages/fxa-event-broker/src/delete-reason/delete-reason.ts	Defines and narrows public reasons.
packages/fxa-event-broker/src/delete-reason/delete-reason.spec.ts	Tests reason validation.
packages/fxa-auth-server/lib/account-delete.ts	Publishes mapped deletion reasons.
packages/fxa-auth-server/lib/account-delete.spec.ts	Tests deletion notifications.
packages/fxa-auth-server/lib/account-delete-reason.ts	Maps internal to public reasons.
packages/fxa-auth-server/lib/account-delete-reason.spec.ts	Tests reason mappings.
libs/payments/webhooks/src/lib/fxa-webhooks.service.spec.ts	Tests reason-bearing and legacy events.
libs/payments/webhooks/src/lib/fxa-webhooks.schemas.ts	Accepts an optional deletion reason.
apps/payments/api/src/scripts/test-fxa-webhook.ts	Adds a reason to test payloads.

Review details

• Files reviewed: 17/17 changed files
• Comments generated: 2
• Review effort level: Balanced

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