HTTP Error 400 when trying to delete Illuminate Bundle

When trying to delete a currently enabled Illuminate bundle, you get an "HTTP 400 Bad Request" error with no additional information. No logs in server.log either.

However, the API Browser explains that a 400 error in this context means that you cannot delete a currently enabled Illuminate bundle. This contextual information should be provided to the user in some obvious fashion without having to dig into the API browser.

I haven't tested this against other API's but this should also apply across every endpoint we have, for the sake of our users.


## Your Environment

* Graylog Version: 6.1.10