Add constants to Woo Subscriptions form component

[MAILPOET-3471]

assets/js/src/segments/dynamic/dynamic_segments_filters/woocommerce_subscription.tsx

@@ -4,20 +4,28 @@ import { assign, compose, find } from 'lodash/fp';
 import Select from 'common/form/react_select/react_select';
 
 import {
-  OnFilterChange, SegmentTypes,
+  OnFilterChange,
+  SegmentTypes,
   SelectOption,
   WooCommerceSubscriptionFormItem,
 } from '../types';
 import { SegmentFormData } from '../segment_form_data';
 
+enum WooCommerceSubscriptionsActionTypes {
+  ACTIVE_SUBSCRIPTIONS = 'hasActiveSubscription',
+}
+
 export const WooCommerceSubscriptionOptions = [
-  { value: 'hasActiveSubscription', label: MailPoet.I18n.t('segmentsActiveSubscription'), group: SegmentTypes.WooCommerceSubscription },
+  { value: WooCommerceSubscriptionsActionTypes.ACTIVE_SUBSCRIPTIONS, label: MailPoet.I18n.t('segmentsActiveSubscription'), group: SegmentTypes.WooCommerceSubscription },
 ];
 
 export function validateWooCommerceSubscription(
   formItems: WooCommerceSubscriptionFormItem
 ): boolean {
-  if (formItems.action === 'hasActiveSubscription' && !formItems.product_id) {
+  if (
+    formItems.action === WooCommerceSubscriptionsActionTypes.ACTIVE_SUBSCRIPTIONS
+    && !formItems.product_id
+  ) {
     return false;
   }
   return true;