Consider throwing an error if `setVersionRequired` and `setDefaultVersion` are called on `ApiVersionConfigurer`

[philwebb]

Currently the ApiVersionConfigurer.setVersionRequired(...) states:

When a defaultVersion is also set, this is automatically set to false.

With Spring Boot property support it's pretty easy set version-required and default-version. I think it might be better to consider this a configuration error and fail startup early.

[rstoyanchev]

We can indeed flag that if both are explicitly set.