* "P1W" grain should respect DATEFIRST setting in MS SQL Server
* Added "week_start_sunday" and "week_start_monday" grains support. Adjusted the "week" grain for better backward compatibility with MS SQL 2005/2008.
* Stylistic and linter-requested changes
* fix test
Co-authored-by: Valeriy Aleksashkin <v.aleksashkin@gmail.com>
Co-authored-by: Ville Brofeldt <ville.v.brofeldt@gmail.com>