title: Jackson force serialization of final fields without annotations
body: <p>I have a class with a private constructor that I cannot modify containing many final fields that I wish to serialize with Jackson. Is there any way to force Jackson to serialize all the final fields?</p>
  
  <p>I've tried using a custom filter provider like so: <code>new ObjectMapper().setFilterProvider(new SimpleFilterProvider().addFilter("serialize-final", SimpleBeanPropertyFilter.serializeAll()))</code> but Jackson seems to filter out the final fields before/after it applies my filter.</p>
  
  <p>The use case is my program depends on a library that uses feature flags to indicate which features are enabled. The distributor of the library has compiled the feature flags into final fields on a singleton object that I am able to access at runtime. I wish to add the ability to dump the feature flags when requested to allow for easier debugging and simply serializing them as JSON seems like the easiest solution.</p>