[web] cleanup archived split-test assignments from user record on login (#33365)

* [web] cleanup archived split-test assignments from user record on login

Co-authored-by: Anna Claire Fields <anna.fields@overleaf.com>

* [migrations] purge archived split tests from all users

Co-authored-by: Anna Claire Fields <anna.fields@overleaf.com>

* [web] add missing mock and update snapshot test

* [web] gracefully access db.users.splitTests

---------

Co-authored-by: Anna Claire Fields <anna.fields@overleaf.com>
GitOrigin-RevId: bd185074a402556d7b7c812208cf834dd52b27a5

tools/migrations/20260504100000_cleanup_users_split_tests.mjs

@@ -0,0 +1,30 @@
+import { db } from './lib/mongodb.mjs'
+import { batchedUpdate } from '@overleaf/mongo-utils/batchedUpdate.js'
+
+const tags = ['saas', 'server-ce', 'server-pro']
+
+const migrate = async () => {
+  const splitTests = await db.splittests.find().toArray()
+  const toCleanup = {}
+  for (const splitTest of splitTests) {
+    if (splitTest.archived) {
+      toCleanup[`splitTests.${splitTest.name}`] = 1
+    }
+  }
+  // Take the easy route and unset all the archived split tests on all the users with any split test assignment.
+  await batchedUpdate(
+    db.users,
+    { splitTests: { $exists: true } },
+    { $unset: toCleanup }
+  )
+}
+
+const rollback = async () => {
+  // The data is gone. Nothing to revert to.
+}
+
+export default {
+  tags,
+  migrate,
+  rollback,
+}