Method comparator

app/collections/Prepaids.js:29–34

(prepaid)

    }

    comparator (prepaid) {
      return [
        prepaid.get('type') === 'course' ? 'C' : 'S',
        prepaid.get('endDate')
      ].toString()
    }

    totalMaxRedeemers () {
      return sum((Array.from(this.models).map((prepaid) => prepaid.get('maxRedeemers')))) || 0