docs: public String getKey(Map<String, String> variableValues)
      {
          StringBuilder key = new StringBuilder();
          for ( ConfigurationKeyPart p : parts )
          {
              if ( p.isVariable() )
              {
                  String value = variableValues.get(p.getValue());
                  if ( value == null )
                  {
                      log.warn("No value found for variable: " + p.getValue());
                      value = "";
                  }
                  key.append(value);
              }
              else
              {
                  key.append(p.getValue());
              }
          }
  
          return key.toString();
      }