Use points to pay order

[Oksana-Voitovych]

As a user I want to use my points to pay my order so that I could have a discount or free of charge payment of ordered items.

Preconditions:
The registered user is logged in
User chose services from the list on “Деталі замовлення” tab

Business rules:
User is able to use points only in full, when the amount of points is less or equal than the total amount to pay.

Acceptance criteria:

1. Under the table with the list of services on the tab “Деталі замовлення” user sees a question “Чи бажаєте Ви скористатися бонусами?” and radio buttons “Yes” and “No”:
   a. user can select only one answer
   b. system displays “No” button by default.

2. User should be able to see the amount of points on his balance under the question field “На Вашому рахунку <кількість> бонусів”.

3. By clicking on the button “Yes” system should recalculate and displays the total amount of the order using a formula, where:
   total amount after using points = total amount - amount of points
   Ex.: 1200 - 200 = 1000 грн

4. When the amount of points is higher than the total amount, user can use the amount points respective to the total amount.
   should be able to see the remaining balance - “залишок на Вашому бонусному рахунку <кількість> бонусів”.

To be discussed:
Points reward system details

Epic: #2195