async process(context) {
      let index = -1;
      const next = async () => {
        index++;
        if (index < this.middlewares.length) {
          await this.middlewares[index](context, next);
        }
      };
      await next();
      return context;
    }
Enumeration of available debug levels from lowest (NONE) to highest (TRACE).
Used to control the verbosity of logging output.