Unique Webhook IDs

[sbuettner]

Is your feature request related to a problem? Please describe.

Connectors currently allow to register multiple webhooks pointing to the same Webhook ID e.g. URL/endpoint. This allows customers to invoke multiple inbound connectors with a single webhook request. This behaviour doesnt provide any transactional safety as one of the inbound connectors could fail while others were executed successfully.

To provide a clearer execution model for customers, the runtime should limit the usage of a single Webhook ID to one inbound connector. The endpoint should also return a non-successful HTTP status code if that connector wasnt executed successfully.

As the runtime cant guarantee uniqueness on the zeebe/operate level it has to do the uniqueness check itself. To allow customers to react to this uniqe constraint violation the runtime should report the inbound webhook connector as DOWN via the health report facilities. This way customers can see errors in the web modeler and refactor their BPMN models accordingly.

Describe the solution you'd like

The runtime keeps an in-memory index of all inbound webhook connectors. The first inbound connector for a Webhook ID will get activated while others that use the same ID will be reported as DOWN.

Describe alternatives you've considered

Keeping the existing multiplexing strategy doesnt provide more value while leading to a confusing transactional model. Therefore the decision was made to only support a 1:1 mapping of an endpoint to an inbound webhook connector.