test(e2e): add multivariate feature toggle and change request tests

Add E2E tests to cover multivariate feature bugs fixed in RTK Query migration:

1. Multivariate Feature Toggle Test:
   - Tests toggling MV features via edit modal works without 400 errors
   - Validates multivariate_feature_state_values transformation

2. Change Request with Multivariate Feature Test:
   - Tests creating change requests with MV features
   - Only runs when segment_change_requests feature is enabled
   - Validates the fix for incorrect multivariate format in CRs

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: talissoncosta

frontend/e2e/tests/flag-tests.ts

@@ -6,9 +6,13 @@ import {
   createRemoteConfig,
   deleteFeature,
   editRemoteConfig,
+  getFlagsmith,
+  gotoFeature,
+  gotoFeatures,
   log,
   login,
   parseTryItResults,
+  setText,
   toggleFeature,
   waitForElementVisible,
 } from '../helpers.cafe';
@@ -84,4 +88,66 @@ export default async function () {
   log('Clear down features')
   await deleteFeature(1, 'header_size')
   await deleteFeature(0, 'header_enabled')
+
+  log('Create multivariate feature for toggle test')
+  await createRemoteConfig(0, 'mv_toggle_test', 'control', 'MV toggle test', false, [
+    { value: 'variant_a', weight: 50 },
+    { value: 'variant_b', weight: 50 },
+  ])
+
+  log('Toggle multivariate feature via edit modal')
+  await gotoFeatures()
+  await click(byId('feature-switch-0-on'))
+  await waitForElementVisible('#create-feature-modal')
+  await click(byId('toggle-feature-button'))
+  await click(byId('update-feature-btn'))
+  await closeModal()
+  await waitForElementVisible(byId('feature-switch-0-off'))
+
+  log('Multivariate toggle test passed')
+  await deleteFeature(0, 'mv_toggle_test')
+
+  const flagsmith = await getFlagsmith()
+  const hasChangeRequests = flagsmith.hasFeature('segment_change_requests')
+
+  if (hasChangeRequests) {
+    log('Create multivariate feature for change request test')
+    await createRemoteConfig(0, 'mv_cr_test', 'control', 'MV CR test', false, [
+      { value: 'variant_a', weight: 50 },
+      { value: 'variant_b', weight: 50 },
+    ])
+
+    log('Enable change requests')
+    await click('#project-settings-link')
+    await click('[data-test="js-change-request-approvals"]')
+    await waitForElementVisible('[name="env-name"]')
+
+    await gotoFeatures()
+
+    log('Open multivariate feature for change request')
+    await gotoFeature(0)
+    await waitForElementVisible('#create-feature-modal')
+    await click(byId('toggle-feature-button'))
+
+    log('Create change request with multivariate feature')
+    await click(byId('update-feature-btn'))
+    await waitForElementVisible('[name="title"]')
+    await setText('[name="title"]', 'Test MV Change Request')
+    await click('#create-cr-btn')
+    await t.wait(1000)
+    await closeModal()
+
+    log('Change request with multivariate feature created successfully')
+
+    log('Disable change requests')
+    await click('#project-settings-link')
+    await click('[data-test="js-change-request-approvals"]')
+
+    await gotoFeatures()
+    await deleteFeature(0, 'mv_cr_test')
+
+    log('Change request test passed')
+  } else {
+    log('Skipping change request test - segment_change_requests feature not enabled')
+  }
 }