feat: enable assignment v2 by default for new accounts (#14031)

## Description

Enable assignment v2 by default for new accounts

## Type of change

- [ ] New feature (non-breaking change which adds functionality)


## Checklist:

- [ ] My code follows the style guidelines of this project
- [ ] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [ ] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

db/migrate/20260409091202_enable_assignment_v2_for_new_accounts.rb

@@ -0,0 +1,14 @@
+class EnableAssignmentV2ForNewAccounts < ActiveRecord::Migration[7.1]
+  def up
+    config = InstallationConfig.find_by(name: 'ACCOUNT_LEVEL_FEATURE_DEFAULTS')
+    return if config&.value.blank?
+
+    features = config.value
+    feature = features.find { |f| f['name'] == 'assignment_v2' }
+    return if feature.blank?
+
+    feature['enabled'] = true
+    config.update!(value: features)
+    GlobalConfig.clear_cache
+  end
+end