code: static Map<String, String> resolveHeaders(Method method) {
      Map<String, String> headerMap = new HashMap<>();
      for (Header header : method.getDeclaringClass().getAnnotationsByType(Header.class)) {
        headerMap.put(header.name(), header.value());
      }
      for (Header header : method.getAnnotationsByType(Header.class)) {
        headerMap.put(header.name(), header.value());
      }
      return headerMap;
    }
docs: 解析请求头