MM-35125 CRT: Mention badge on threads doesn't appear until refresh (#17504)

store/store.go

@@ -272,6 +272,8 @@ type ChannelMemberHistoryStore interface {
 	PermanentDeleteBatch(endTime int64, limit int64) (int64, error)
 }
 type ThreadStore interface {
+	GetThreadFollowers(threadID string) ([]string, error)
+
 	SaveMultiple(thread []*model.Thread) ([]*model.Thread, int, error)
 	Save(thread *model.Thread) (*model.Thread, error)
 	Update(thread *model.Thread) (*model.Thread, error)