code: public String getString(Key key, String defaultValue) {
          return getString(key.toString(), defaultValue);
      }
docs: Retrieves a configuration value with the given key constant (e.g. Key.APPLICATION_NAME)
  
  @param key The key of the configuration value (e.g. application.name)
  @param defaultValue The default value to return of no key is found
  @return The configured value as String or the passed defautlValue if the key is not configured