v1.5.3
* refactor: distinguish between Unique and UniqueIndex * rewrite MigrateColumnUnique * update gorm to master latest (for https://github.com/go-gorm/gorm/pull/6386)
* refactor: distinguish between Unique and UniqueIndex * rewrite MigrateColumnUnique * update gorm to master latest (for https://github.com/go-gorm/gorm/pull/6386)