[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

services/web/test/unit/src/Authentication/AuthenticationController.test.mjs

@@ -102,6 +102,17 @@ describe('AuthenticationController', function () {
       })
     )
 
+    vi.doMock(
+      '../../../../app/src/Features/SplitTests/SplitTestHandler',
+      () => ({
+        default: (ctx.SplitTestHandler = {
+          promises: {
+            userMaintenanceOnLogin: sinon.stub().resolves(),
+          },
+        }),
+      })
+    )
+
     vi.doMock('../../../../app/src/Features/User/UserUpdater', () => ({
       default: (ctx.UserUpdater = {
         updateUser: sinon.stub(),