request help: jwt功能只做token验证，关闭获取token的接口

[wjmmjr]

Issue description

能不能开启jwt功能，关闭获取jwt token的接口，客户自己根据我们提供的key等信息自己生成token，我们只做token验证

Environment

• apisix version (cmd: apisix version):
• OS (cmd: uname -a):
• OpenResty / Nginx version (cmd: nginx -V or openresty -V):
• etcd version, if have (cmd: run curl http://127.0.0.1:9090/v1/server_info to get the info from server-info API):
• apisix-dashboard version, if have:
• the plugin runner version, if the issue is about a plugin runner (cmd: depended on the kind of runner):
• luarocks version, if the issue is about installation (cmd: luarocks --version):

[laokan]

curl -i -X PUT \ -H "Content-Type:application/json" \ -H "X-API-KEY:edd1c9f034335f136f87ad84b625c8f1" \ -d \ '{ "interceptors": [ { "name": "ip-restriction", "conf": { "whitelist": ["10.0.0.0/8"] } } ] }' \ 'http://apisix:9080/apisix/admin/plugin_metadata/prometheus'

可以利用 interceptors 把url 保护一下