[history-v1] add endpoint for downloading latest zip (#33181)

* [history-v1] add endpoint for downloading latest zip

* [web] address review feedback

* [web] tests: do not overwrite db.projects.overleaf, extend it

* [web] set includeReferer flag from downloading zip

GitOrigin-RevId: e63e549f004230086f82eccf03b43fd62bde6071

services/web/app/src/Features/SplitTests/SplitTestHandler.mjs

@@ -333,6 +333,30 @@ async function getOneTimeAssignment(splitTestName) {
   }
 }
 
+/**
+ * Checks if a feature flag is enabled for a specific user
+ *
+ * Retrieves the feature flag assignment for a user and determines if the assigned variant is 'enabled'
+ *
+ * @param req the request
+ * @param res the Express response object
+ * @param {string} splitTestName - The unique name of the feature flag
+ * @param {Object} options
+ * @param {boolean} options.includeReferer For ajax requests and downloads include the split test overrides of the page
+ * @returns {Promise<boolean>} True if the user's assigned variant is 'enabled', false otherwise
+ */
+async function featureFlagEnabled(
+  req,
+  res,
+  splitTestName,
+  { includeReferer = false } = { includeReferer: false }
+) {
+  const { variant } = await getAssignment(req, res, splitTestName, {
+    includeReferer,
+  })
+  return variant === 'enabled'
+}
+
 /**
  * Checks if a feature flag is enabled for a specific user
  *
@@ -997,6 +1021,7 @@ export default {
   getPercentile,
   getAssignment: callbackify(getAssignment),
   getAssignmentForUser: callbackify(getAssignmentForUser),
+  featureFlagEnabled: callbackify(featureFlagEnabled),
   featureFlagEnabledForUser: callbackify(featureFlagEnabledForUser),
   getOneTimeAssignment: callbackify(getOneTimeAssignment),
   getActiveAssignmentsForUser: callbackify(getActiveAssignmentsForUser),
@@ -1006,6 +1031,7 @@ export default {
   promises: {
     getAssignment,
     getAssignmentForUser,
+    featureFlagEnabled,
     featureFlagEnabledForUser,
     getOneTimeAssignment,
     getActiveAssignmentsForUser,