For some strange reason in so very configurable OroCommerce there is no ability to manage product units and the only few words doc says that its possible to add units via web api. I need to add "days" units and best if do it in code via migration. Is it enough just to make migration like
INSERT INTO `oro_product_unit` (`code`, `default_precision`) VALUES ('day', '0');
and add tranlation messages like
oro.product_unit.day.label.full: day
oro.product.product_unit.day.label.full: day
or need to do smth else?
Product units may be loaded to the database using the data fixtures, like this one that loads default units: https://github.com/oroinc/orocommerce/blob/4.2.1/src/Oro/Bundle/ProductBundle/Migrations/Data/ORM/LoadProductUnitData.php#L47-L52
In addition, you have to provide translations for the new unit, but there are more messages then you specified in the question: https://github.com/oroinc/orocommerce/blob/ad94fe9bd63db28eae7d4a73743a4cada4f49080/src/Oro/Bundle/ProductBundle/Resources/translations/jsmessages.en.yml#L26-L35