docs: public void set(final String originalKey, final Object object) {
          final String key = applicationName + "." + originalKey;
          if (object == null || (object instanceof String && ((String) object).length() == 0)) {
              // remove
              application.setConfig(application.getConfig().withoutPath(key));
          } else {
              // create or update
              ConfigValue value = ConfigValueFactory.fromAnyRef(object, "modified at runtime ");
              application.setConfig(application.getConfig().withValue(key, value));
          }
          // merge global config (no reloading)
          config = application.getConfig().withFallback(user.getConfig()).withFallback(system.getConfig());
      }