All tickets must be configured as "personalized", with the exception of
"add-ons", and an add-on is recognized by its category. The use-case
for non-personalized add-on tickets was Devconnect towels.
To date, we only care about categories for the purpose of ensuring that
non-personalized tickets are, indeed, add-ons. No category data is persisted,
as it's used only for validation.
All tickets must be configured as "personalized", with the exception of "add-ons", and an add-on is recognized by its category. The use-case for non-personalized add-on tickets was Devconnect towels.
To date, we only care about categories for the purpose of ensuring that non-personalized tickets are, indeed, add-ons. No category data is persisted, as it's used only for validation.
Category API docs: https://docs.pretix.eu/en/latest/api/resources/categories.html
See #1119 for original implementation.