[Feature Request] Disallow unknown keys in verify

[akx]

Describe the feature request

Related to #3757 (validating the configuration against a strict schema).

frpc verify doesn't validate the presence of extraneous/unknown keys in the document given, so typos are easily uncaught. Can you spot at least 4 in the document below? 😁

$ cat > config.json
{
  "serverAddr": "localhost",
  "serverPort": 7000,
  "auth": {
    "metho": "oidc"
  },
  "log": {
    "leverl": "trace"
  },
  "proxies": [
    {
      "name": "xxx",
      "type": "http",
      "localPort": 8888,
      "customDomains": [
        "xxx"
      ],
      "transpor": {
        "useEncrypion": true,
        "useCompression": true
      }
    }
  ]
}
$ ./frpc verify -c a.json
frpc: the configuration file a.json syntax is ok
$

Describe alternatives you've considered

No response

Affected area

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

[fatedier]

I think it is ok to add a --strict-mode option to enable this feature, with schema validation disabled by default.