code: protected static ObjectMapper buildObjectMapperForDeserialization() {
          final ObjectMapper mapper = new ObjectMapper();
          mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
          return mapper;
      }
docs: This is static, so really there is no true overriding it in subclasses.
  However, fromJSON will do the proper reflection in order to invoke
  the proper method for the class that is being deserialized. So subclasses
  that want to provide their own ObjectMapper will define their own
  method that matches the signature of this method and it will be used.
  
  @return object mapper to be used for deserializing JSON.