Issue description

Environment

Bug report without environment information will be ignored or closed.

• apisix version (cmd: apisix version): 2.7
• OS (cmd: uname -a): Darwin Kernel Version 20.3.0
• OpenResty / Nginx version (cmd: nginx -V or openresty -V): openresty/1.19.3.1
• etcd version, if have (cmd: run curl http://127.0.0.1:9090/v1/server_info to get the info from server-info API): 3.4.0
• apisix-dashboard version, if have: NAN
• luarocks version, if the issue is about installation (cmd: luarocks --version): NAN

Minimal test code / Steps to reproduce the issue

Bug report without steps to reproduce will be ignored or closed.

1. I have a consumer, username is user
   

2. when I update this consumer by admin-api used mismatched username in path and body, update successfully

What's the actual result? (including assertion message & call stack if applicable)

What's the expected result?

IMO it should return HTTP code 400 when call admin-api to update consumer with mismatched username in path and body or user will get confused.