- Migrate from deprecated sources API to modern payment_methods API in SubscriptionsController
- Update subscription plan modifications to use Subscription.modify instead of direct assignment
- Fix payment method creation/deletion to use PaymentMethod.create/detach instead of sources
- Update view templates to use new payment_methods data structure
- Migrate price.id usage from deprecated plan.id in data integrity tasks
- Add comprehensive test suite with proper Stripe API stubs
- Add missing test gems: rspec-rails, webmock, factory_bot_rails, shoulda-matchers
This resolves Error 500 when users try to upgrade to Premium subscriptions.
The original error was: NoMethodError - undefined method 'total_count' for nil:NilClass
caused by stripe_customer.sources.total_count when sources API returned nil.
🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>
