def booker_must_be_booker
        if booker.present? && !booker.class.booker?
          errors.add(:booker, T.er('booking.booker_must_be_booker', model: booker.class.to_s))
        end
      end
def booker_must_be_booker
        if booker.present? && !booker.class.booker?
          errors.add(:booker, T.er('booking.booker_must_be_booker', model: booker.class.to_s))
        end
      end
Validation method. Check if the booker model is actually a booker