v1 API Refactoring

In order to maintain and extend Tacker continuously, it's important to improve the maintainability of the v1 API. As v1 API has many pain points such as tightly coupled classes and dependency between DB tables, it's difficult to fix it by partial refactoring. To solve this problem, this blueprint proposes refactoring based on v2 API architecture. In other words, adding a new v1 API by copying the v2 API and modifying it for a v1 compliant API.