code: public static void configureMapper(ObjectMapper mapper, Application.Mode mode) {
          mapper.registerModule(new GuavaModule());
          mapper.setSerializationInclusion(JsonInclude.Include.NON_EMPTY)
                  .enable(SerializationFeature.WRITE_ENUMS_USING_INDEX)
                  .enable(MapperFeature.PROPAGATE_TRANSIENT_MARKER)
                  .disable(
                          SerializationFeature.WRITE_NULL_MAP_VALUES,
                          SerializationFeature.FAIL_ON_EMPTY_BEANS
                  );
          if (!mode.isDev()) {
              mapper.disable(
                      DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES
              );
          }
      }
docs: <p>configureMapper.</p>
  
  @param mapper a {@link com.fasterxml.jackson.databind.ObjectMapper} object.
  @param mode   App mode