do not remove invoiced fees

constants/constants.js

@@ -119,6 +119,8 @@ const discounts = {
 };
 const DISCOUNT_PLANS = process.env.DISCOUNT_PLANS.split(',').map(planName => planName.trim()) || [];
 
+const UNPAID_FEE_STATUS = 'not_paid';
+
 module.exports = {
     VALID_CSV_HEADERS,
     USER_ENTRY_EVENT,
@@ -141,4 +143,5 @@ module.exports = {
     ALLOWED_BOOKING_CANCELLATION_TIME,
     discounts,
     DISCOUNT_PLANS,
+    UNPAID_FEE_STATUS,
 };