[BUG] I want to modify the content-type of returning data, but the modified Content-Type cannot take effect

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Current Behavior

in this case, HTTP return json data, I want to change to the return format of XML, but the Content-Type cannot be modified.

### Expected Behavior

i can change the response header in exchange,
`exchange.getResponse().getHeaders().setContentType(xxx)`

### Steps To Reproduce

modify the body and header of response.
return changed body but the content-type of response header un-changed

### Environment

```markdown
ShenYu version(s):
master
```

### Debug logs

_No response_

### Anything else?

content-type use single method to require, However, it is not obtained from exchange but from Attribute,

when i add this line code ,it can fix ,is it correct?

Start with the response handling path described in the issue: modify both the response body and headers through exchange.getResponse().getHeaders(), then compare the returned Content-Type with the requested XML format. Check why Content-Type is read from an Attribute instead of the exchange response headers; done means the modified response uses the new Content-Type consistently.

Written by the indexing model from the issue text.