[MM-23264] Get channel member counts by group (#14068)

* MM-23264 Add api endpoint for get groups with members in channel

Add store tests

Add tests for api func

Gofmt

Apply changes from code review

* MM-23264 Make store layers

* MM-23264 Check read permission on channel member counts

* Trigger CI

store/timer_layer.go

@@ -1032,6 +1032,22 @@ func (s *TimerLayerChannelStore) GetMemberCountFromCache(channelId string) int64
 	return resultVar0
 }
 
+func (s *TimerLayerChannelStore) GetMemberCountsByGroup(channelID string, includeTimezones bool) ([]*model.ChannelMemberCountByGroup, *model.AppError) {
+	start := timemodule.Now()
+
+	resultVar0, resultVar1 := s.ChannelStore.GetMemberCountsByGroup(channelID, includeTimezones)
+
+	elapsed := float64(timemodule.Since(start)) / float64(timemodule.Second)
+	if s.Root.Metrics != nil {
+		success := "false"
+		if resultVar1 == nil {
+			success = "true"
+		}
+		s.Root.Metrics.ObserveStoreMethodDuration("ChannelStore.GetMemberCountsByGroup", success, elapsed)
+	}
+	return resultVar0, resultVar1
+}
+
 func (s *TimerLayerChannelStore) GetMemberForPost(postId string, userId string) (*model.ChannelMember, *model.AppError) {
 	start := timemodule.Now()