docs: function promesso (handler) {
    const handleFn = isFunction(handler) ? [handler] : handler;
    const middlewares = [];
    let validations = 0;
  
    handleFn.forEach(h => {
      if (!isFunction(h)) throw new Error('Handler is expected to be a function or an Array of functions.');
  
      if (isObject(handleFn['@validation'])) {
        middlewares.push(validation(h['@validation']), validationMiddleware);
        if (++validations > 1) throw new Error('Every handler can have only one validator per chain.');
      }
  
      middlewares.push(h);
    });
  
    return middlewares.map(rawOrPromise);
  }