有办法修改响应头的content-type属性吗

在 common/common-rest/src/main/java/org/apache/servicecomb/common/rest/filter/inner/ServerRestArgsFilter.java 中
处理响应体Content-Type属性的方法是通过拼接produceProcessor的getName()方法返回的值和"; charset=utf-8"字符串实现的，但如果我需要设置其他charset，甚至添加boundary属性，应该怎么做？
``` java
responseEx.setContentType(produceProcessor.getName() + "; charset=utf-8");
```
比如我某个契约需要：
Content-Type: multipart/form-data; boundary=----------------------

Start in common/common-rest/src/main/java/org/apache/servicecomb/common/rest/filter/inner/ServerRestArgsFilter.java at the responseEx.setContentType call, then trace produceProcessor.getName() and the response handling around it. Determine how response media-type parameters are represented and where existing REST tests cover this path. Done means callers can produce the requested charset and boundary parameters instead of always receiving charset=utf-8.

Written by the indexing model from the issue text.