Webhook: do not throw NullPointerException when the correlation key is in wrong format

[markfarkas-camunda]

Describe the Bug

If we define Correlation key (payload) in the wrong format, we get a 500 error message in response. This is wrong because of 2 reasons:

1. It is not helpful at all, and makes it impossible to users to figure out what to fix and how. I know because I had the exact same issue, and spent an hour figuring out what is wrong.
2. We get the 500 because we have a NullPointerException in the backend. We should handle the case when the correlation key is not in the right format.

Steps to Reproduce

1. Run the bpmn diagram below.
2. Observe the 500 error throwns by the REST connector

WRONG_webhook-intermediate-event-secrets-test.bpmn.txt

Screens

Expected Behavior

We should not throw a NullPointerException on the backend for this configuration, and should send back more information about what went wrong to the client.

Environment

• SaaS (8.3.0)
• Self Managed:
  • OS: Windows 11
  • Camunda version: 8.3.0

[sbuettner]

I agree, we should have a proper error code like CORRELATION_KEY_EXPRESSION_FAILED or similar.