Docs: Feedback for Using the REST Endpoint Groups

Hi, I have some feedback about [this page](https://github.com/hazelcast/imdg-docs/edit/v/3.12/docs/modules/management/pages/rest-endpoint-groups.adoc)

I was trying to call the endpoint
/hazelcast/rest/log-level (POST)

however, it returns this message:
```
{
"status": "fail",
"message": "This endpoint expects at least 3 parameters"
}
```

but in the above documentation, i could not see any sample usage nor parameters documented on how to properly invoke this API.
Is there a place where all of these are documented? The REST endpoint group doc just listed all API's but no description how to properly invoke.