OBGM-687 price and package issue in product source import (#4271)
* OBGM-687 Change default value of a product package price on product source import
add database migration to remove package price FK for records that don't exist
* OBGM-687 Fixes after review
- change changelog migration name
- add comment explaining the migration
- allow cratation of productPackages with null productPrice (remove default value 0)
- do not render currency when productPrice is null on productSupplier tabs
* OBGM-687 Add an empty option on parent category select
