Fix: 'Number of times the offer can be used' (RTC-31810)

An offer is correctly saved in the database when creating a new promotion and price rule has 'Number of times the offer can be used' set as editable in offer. This resolves issue related to being unable to submit promotion with such offer.

Import of customer groups (RTC-29008)

Customer groups are imported into the Promotion database each time an edit or new entry is made in CustomerService.