Document or provide examples for more complex error handling

Hello! I am new to Rust and have recently learned about okapi. I am trying to use it for a REST API with a mongodb backend. I would like to properly handle and report mongodb-related failures as a HTTP 500 error, but I cannot figure out how to do that. I suppose I could implement OpenApiResponder for the mongodb errors, but it is not clear to me how to properly implement or how I would set up the return type for my handler. An example or more documentation would be very helpful =)