I like this package, because I know what a hassle the exception_handler can be.
I was wondering if you would consider moving to a more standardized format, like for example problem+json? This can of course be done as a setting.
Explanation problem+json: https://lakitna.medium.com/understanding-problem-json-adf68e5cf1f8. Specs: https://datatracker.ietf.org/doc/html/rfc7807