milestone.3 已完成
代码仓库： GitHub - invisibook-lab/invisibook at proof_of_buy · GitHub
检验方式： invisibook/docs/milestones/test_guide_3.md at proof_of_buy · invisibook-lab/invisibook · GitHub
完整设计文档： invisibook/docs/proof_of_buy_en.md at proof_of_buy · invisibook-lab/invisibook · GitHub