@type category() :: :national | :federal | :regional | :religious | :other

@type country_code() :: atom()

@type region() :: atom()

@type t() :: %Holidex.Holiday{
  categories: [category()],
  country: country_code(),
  date: Date.t(),
  description: String.t() | nil,
  name: String.t(),
  observance_date: Date.t(),
  regional_names: %{required(region()) => String.t()},
  regions: [region()] | :all
}