Promo codes are case sensitive

[JosephTico]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. Create event, add new promo code
2. When entering promo code, the admin UI will auto convert the code to uppercase
3. Go to the event page, enter promo code in lowercase
4. Promo code is invalid

Expected behavior
Promo code should be valid independently of case, and if the UX in the admin page is to auto convert to uppercase, it should also do the same in the user interface.