Improve dev experience of creating custom ProblemPostProcessor

[morgenthum]

I want to implement a ProblemPostProcessor and need access to the original exception. The ProblemContext is passed to the apply-Method, but it's fields, including cause, is package scoped.

It would be nice to provide getters for the fields in the ProblemContext class.

[mbechto]

We are in need of this as well, as it would make a lot of nice use cases possible.

Btw. what is the intended way of registering ProblemPostProcessors at runtime?

[lwitkowski]

I've slightly changed the title to make the scope of this issue a bit bigger:

• access fields of ProblemContext (addressed by @chberger in Make ProblemContext fields public #311)
• addressing what is the intended way of registering ProblemPostProcessors at runtime? question from @mbechto, which I'm working on right now, stay tuned.

[lwitkowski]

@morgenthum @mbechto, happy to report that v3.1.0 with this feature is now available in Maven Central, let me guys now how it works for you.

[mbechto]

Great news, thanks @lwitkowski! We will test it and report back to you soon.