[Feature Request] Expose proxy information as prometheus metric

[RobKenis]

Describe the feature request

Add a prometheus metric frp_server_proxy_info{name, type, client_version} with information that is also exposed in the dashboard. This way I can include the client version in the same Grafana dashboard as my other FRP statistics.

Describe alternatives you've considered

Can I create a custom plugin to expose this information?

Affected area

• [ ] Docs
• [ ] Installation
• [ ] Performance and Scalability
• [ ] Security
• [ ] User Experience
• [ ] Test and Release
• [ ] Developer Infrastructure
• [ ] Client Plugin
• [ ] Server Plugin
• [ ] Extensions
• [X] Others

[fatedier]

The current implementation is not very elegant. The client_version should not actually be the metadata of the proxy. There should be a separate client/host object, and the proxy should be associated with this object.

We need to rethink the best implementation method here. We did not previously expose the client dimension object to the user, so this change may not be very simple.