### Enum extensibility
Every enum-shaped field in this document is an **open enum**: the listed values
are the complete current set, but NOB may add new ones in a future, backward
compatible release. Integrators **must not** reject a payload, or the webhook
delivery, solely because it contains a value they do not yet recognize — unknown
values should be tolerated (e.g. logged and treated as a generic/unmapped
variant) rather than causing a hard failure.