[Feature Request] add metadatas to `frpc` proxy commands

[morph027]

Describe the feature request

If we are using the server plugin for e.g. multiple user auth, it would be nice to be able to use the cli command with commandline params instead of a config file. Therefore we need to make sure to provide metadatas.

Probably something like frpc http --user bar --metadatas token=foo ... (see https://github.com/spf13/pflag/pull/133/) ?

Describe alternatives you've considered

No response

Affected area

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

[fatedier]

I think it's okay.