Implement interstitial payment page for free trial button on project page with split test (#8311)

GitOrigin-RevId: b24b4f91d281c2756aed68ec176d138fcdd52e54

services/web/frontend/js/main/account-upgrade.js

@@ -1,4 +1,9 @@
 import * as eventTracking from '../infrastructure/event-tracking'
+import getMeta from '../utils/meta'
+
+const interstitialPaymentAfterPaywallVariant =
+  getMeta('ol-splitTestVariants')?.['interstitial-payment-from-paywall'] ??
+  'default'
 
 function startFreeTrial(source, version, $scope) {
   const plan = 'collaborator_free_trial_7_days'
@@ -11,7 +16,12 @@ function startFreeTrial(source, version, $scope) {
     }
     eventTracking.sendMB('paywall-click', { 'paywall-type': source })
 
-    url = `/user/subscription/new?planCode=${plan}&ssp=true`
+    if (interstitialPaymentAfterPaywallVariant === 'active') {
+      url = '/user/subscription/choose-your-plan'
+    } else {
+      url = `/user/subscription/new?planCode=${plan}&ssp=true`
+    }
+
     url = `${url}&itm_campaign=${source}`
     if (version) {
       url = `${url}&itm_content=${version}`