As a breaking change, we can simplify the input by splitting the logger option into multiple and dedicated properties:

After writing my comments around a simplification suggestion around the validateLogger function I have determined that we need to re-think how we deal with this issue.

It was a mistake (that I am responsible for) to accept either an object of options or an instance for the logger property. It's a simpler UX, but basically impossible to handle in a concise and maintainable way with the new throwing requirement. I think it is a good idea to introduce the throwing requirement. But I think it means we need to:

1. Deprecate support for { logger: <logger_instance> }.
2. Introduce { loggerInstance: <logger_instance> }.
3. If loggerInstance is provided, it takes precedence over { logger: <options> }.

The other avenue is to deprecate { logger: <options> }, but I am quite certain that more people pass in options than they do logger instances. We'd break many more people with this avenue.

Originally posted by @jsumners in #4520 (review)