Let user choose in admin UI which discount will be used in the offer

[ricardobrg]

As a user
I want to choose which discount will be used in the offer
so that I can organize my campaigns easily in the admin UI

What it is now

The last discount is used in the offer.

What it should be

A dropdown list of all active discounts should be shown and the user can select which one will be used.

Technical details

Add a dropdown list in home admin UI with the TIKI discounts. Try to make a direct graphql call with the session token. If not possible, create a new endpoint to get all the dicounts from the backend. Let the user change the current active discount and save it to app metadata.

Acceptance criteria

1. The user can change the offer discount in the admin ui
2. This discount is used in the offers