feat: Prometheus can auto set port (#2943)

* feat: config

* feat: prometheus auto set port

pkg/common/prommetrics/discovery.go

@@ -0,0 +1,31 @@
+package prommetrics
+
+import "fmt"
+
+const (
+	APIKeyName             = "api"
+	MessageTransferKeyName = "message-transfer"
+)
+
+type Target struct {
+	Target string            `json:"target"`
+	Labels map[string]string `json:"labels"`
+}
+
+type RespTarget struct {
+	Targets []string          `json:"targets"`
+	Labels  map[string]string `json:"labels"`
+}
+
+func BuildDiscoveryKey(name string) string {
+	return fmt.Sprintf("%s/%s/%s", "openim", "prometheus_discovery", name)
+}
+
+func BuildDefaultTarget(host string, ip int) Target {
+	return Target{
+		Target: fmt.Sprintf("%s:%d", host, ip),
+		Labels: map[string]string{
+			"namespace": "default",
+		},
+	}
+}