Feature request: Consumer groups state metrics

[Rabbit-st]

There are five states, which you can see in kafka's source code. The details are:

• Empty
• Stable
• PreparingRebalance
• CompletingRebalance
• Dead

Use different numbers to represent the state, such as:

0：Empty
1：Stable
2：PreparingRebalance
3：CompletingRebalance
4：Dead 

The code to obtain the status can be referred to:

package main

import (
    "fmt"
    "log"

    "github.com/IBM/sarama"
)

func main() {
    // Kafka broker list
    brokers := []string{"10.100.1.1:9092"}

    // Create a new Sarama config
    config := sarama.NewConfig()
    config.Version = sarama.V2_0_0_0

    // Create a new Sarama admin client
    admin, err := sarama.NewClusterAdmin(brokers, config)
    if err != nil {
        log.Fatalf("Error creating cluster admin: %v", err)
    }
    defer admin.Close()

    // Get all Consumer Groups
    groups, err := admin.ListConsumerGroups()
    if err != nil {
        log.Printf("Error listing consumer groups: %v", err)
        return
    }

    for group := range groups {
        // describe consumer group
        description, err := admin.DescribeConsumerGroups([]string{group})
        if err != nil {
            log.Printf("Error describing consumer group %s: %v", group, err)
            continue
        }

        for _, desc := range description {
            var stateValue float64
            switch desc.State {
            case "Stable":
                stateValue = 1
            case "PreparingRebalance":
                stateValue = 2
            case "CompletingRebalance":
                stateValue = 3
            case "Dead":
                stateValue = 4
            default:
                stateValue = 0
            }
            fmt.Printf("Consumer Group: %s, State: %s, State Value: %f\n", group, desc.State, stateValue)
        }
    }
}