help request: how to set the response content-type

[yunduansing]

Description

when use ext-plugin-post-resp to wrap the response data,client received the response header["Content-Type"] will be changed ,the origin is application/json,but the received of client is text/plain

Environment

• APISIX version (run apisix version):3.0.0
• Operating system (run uname -a):
• OpenResty / Nginx version (run openresty -V or nginx -V):
• etcd version, if relevant (run curl http://127.0.0.1:9090/v1/server_info):
• APISIX Dashboard version, if relevant:
• Plugin runner version, for issues related to plugin runners:
• LuaRocks version, for installation issues (run luarocks --version):

[tzssangglass]

ref: #8388 (comment)

we can tracing in #8388

[github-actions]

This issue has been marked as stale due to 350 days of inactivity. It will be closed in 2 weeks if no further activity occurs. If this issue is still relevant, please simply write any comment. Even if closed, you can still revive the issue at any time or discuss it on the dev@apisix.apache.org list. Thank you for your contributions.

[github-actions]

This issue has been closed due to lack of activity. If you think that is incorrect, or the issue requires additional review, you can revive the issue at any time.