Piece rate support in Check API

You can now support payroll for employees who require to be paid at a fixed piece rate for piecework (ie. each unit produced, mileage driven, or times an action is performed), rather than the hours spent completing the work. We’ve added piece rate specific earning types such as `piece`, `rest_and_recovery`, and `non_productive`, which will allow you to compliantly support piece rate pay in your payroll build. 

Learn more about Piece rate here.