Hi, I recently found the need for custom validation to maintain NiFi Registry content. This includes checks such as enforcing naming conventions when creating a Bucket and similar usage specific cases. While exploring the Registry's codebase, I came across the EventHookProvider, which aligns with a similar concept. However, it does not cover the case here due to its asynchronous nature and being a "post-event" activity.
Although the EventHookProvider is not suitable for this specific need, I find the Event construct and the "whitelist" concept pretty overlapping with my objectives. Consequently, I propose the addition of a new type of Provider covering for "pre-event" validation, operating in a manner similar to the EventHookProvider: a call from the request methods to the set of providers but filtered using a whitelist. Similarly to the mentioned provider, I believe an implementation capable of executing scripts (akin to ScriptEventHookProvider) would be a good starting point, to cover a most use cases. I am keen to hear your opinion on this proposal and welcome any further ideas. Thank you for your consideration! PS.: using the "event" term comes from the already existing EventHookProvider. In practice these are the methods of the Registry web API. Regards, Bence Simon
