Finished User Steps Webhook

You are an expert backend engineer integrating the IDWise Finished User Steps Webhook.

Before writing any code, ask me which backend stack, language, and framework I am using. Examples: Node.js with Express, Python with FastAPI, Python with Django, C# with ASP.NET, Java with Spring Boot, PHP with Laravel, Ruby on Rails, or another stack.

After I answer, generate a complete webhook handler for that stack.

This webhook means the user has submitted all required journey steps, such as document capture and selfie capture, but IDWise may still be processing the submissions. Do not treat systemDecision in this webhook as the final verification decision. If final approval, rejection, or referral handling is required, wait for the Finished Journey webhook instead.

The webhook handler must:

1. Expose an HTTP POST endpoint that receives the IDWise Finished User Steps webhook payload.
2. Parse the JSON payload without failing if IDWise adds extra fields in the future.
3. Read these fields from the payload:
   - event
   - body.eventId
   - body.journeyId
   - body.referenceNo
   - body.systemDecision
4. Validate that the event value is Finished User Steps before processing the payload.
5. Log that the Finished User Steps webhook was triggered, including:
   - eventId
   - journeyId
   - referenceNo
   - systemDecision as the current non-final status
6. Use eventId as an idempotency key so duplicate delivery attempts do not start the same downstream task more than once.
7. Return HTTP 200 to IDWise as soon as the payload is accepted and basic validation is complete.
8. Do not fetch journey details, fetch images, run face matching, run external checks, or update the customer system before returning HTTP 200.
9. After returning HTTP 200, invoke an asynchronous method or background job named processFinishedUserSteps or an equivalent name for the selected stack.
10. In the asynchronous method, fetch the journey details from IDWise using the journeyId, fetch any required submitted images or documents, and then run submission-complete tasks that do not require the final IDWise verification decision.
11. Include examples for these Finished User Steps use cases where relevant:
   - Trigger a face comparison between the submitted selfie and an image from the customer database or a third-party source.
   - Start backend verification tasks such as address verification or credit checks in parallel with IDWise processing.
   - Update the user experience by marking the submission as received and processing in the customer system.
   - Write an audit log recording when the user completed all required steps, including eventId, journeyId, and referenceNo.
12. Add error handling and logging inside the asynchronous method so processing failures are recorded without causing IDWise webhook delivery to time out.
13. Keep IDWise API credentials out of source code by using environment variables or the stack's secret-management approach.

Return:

1. A short implementation checklist.
2. Complete runnable webhook handler code for the selected stack.
3. The asynchronous processFinishedUserSteps method or background job code.
4. Required environment variables.
5. Example log output for a successful webhook trigger, including journeyId, referenceNo, and the current systemDecision.
6. Notes explaining why the handler returns HTTP 200 before fetching journey details, fetching images, or running downstream checks.
7. Notes explaining that the Finished User Steps webhook is not the final verification result and that final decision handling belongs in the Finished Journey webhook.

Do not build this as a frontend handler. The webhook endpoint must run on a trusted backend.