Fastapi-efficient-sql

Added
- New method `select_one_record` of `BaseManager`. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/commit/fc77cdf83f1ec53a1ed5fbef9573717d5ce5843f)
- New parameter `index` of `SQLizer.select_custom_fields`.

Improved
- Switch virtual environment management to `Poetry`. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/pull/3/commits/d18b60ae444236cb4f230e3d8e45bb86761f3646)
- Fix wrong use of `asynctest`. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/pull/3/commits/5763ce8782c9b8d189762b56c8cb85ca2ab1932f)

Added
- Testing supported by `unittest`, `asynctest` and `pytest`.
- New parameter `offset` of `SQLizer.select_custom_fields`. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/commit/698539f332823e1402fbf7c219f506614b94e685)

Improved
- Check `model` of managers and table of `model.Meta` first. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/commit/13fc7fd32fc261437b80a13a6e47f73588183d38)
- Decorator `timing` supports both sync and async functions. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/commit/316f8a3646de74f421a24cd8eb4a721400e3430f)

Added
- Singleton metaclass. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/commit/e16c710ef6b36ba743bb7cb6533ade0b5f78ca8c)
- Import `Q` from `Tortoise-ORM`. [Here](https://github.com/NightMarcher/fastapi-efficient-sql/commit/bb53f892cbe328d02e521e5d63fbd7215cc91ee6)

Changed
- Rename to `SQLizer.sqlize_value`.
- Make SQL more compact.