Sync email to Stripe when user changes email address

[jeremy]

Summary

When the account owner's email changes, the Stripe customer record now gets updated automatically. This handles two scenarios:

1. Owner changes their email - identity_id change on the owner user
2. Ownership transfer - a different user becomes the owner

Root cause: create_stripe_customer set email once at subscription creation time with no subsequent syncing.

Fix: Layered responsibility across User → Account → Subscription:

• User::NotifiesAccountOfEmailChange - Triggers on owner email or role change
• Account::Billing#owner_email_changed - Enqueues background job
• Account::Subscription#sync_customer_email_to_stripe - Updates Stripe customer
• Account::SyncStripeCustomerEmailJob - Async with polynomial backoff retry

Changes

• saas/app/models/user/notifies_account_of_email_change.rb - User concern
• saas/app/models/account/billing.rb - Account method to enqueue job
• saas/app/models/account/subscription.rb - Stripe sync method
• saas/app/jobs/account/sync_stripe_customer_email_job.rb - Background job
• saas/lib/fizzy/saas/engine.rb - Include concern in User
• saas/test/models/user/notifies_account_of_email_change_test.rb - User tests
• saas/test/models/account/billing_test.rb - Job enqueueing tests
• saas/test/models/account/subscription_test.rb - Sync method tests

Test plan

• bin/rails test saas/test/ - All saas tests pass
• Manual: Change email in dev with Stripe integration, verify customer updated
• Manual: Transfer ownership, verify new owner's email synced

Fixes BUG-9504334396
Source: HackerOne #3522917

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[jeremy]

What about account ownership changes? It's not just the owning user's email changed, it's the the account owner email changed.

[Copilot]

Pull request overview

This PR implements automatic syncing of the account owner's email to Stripe when the owner changes their email address or when ownership is transferred to a different user. Previously, the Stripe customer email was only set once at subscription creation time and never updated.

Changes:

• Added User::NotifiesAccountOfEmailChange concern that triggers when owner identity changes or a user becomes owner
• Added Account::Billing#owner_email_changed method to enqueue sync jobs
• Added Account::Subscription#sync_customer_email_to_stripe to update Stripe customer records
• Added Account::SyncStripeCustomerEmailJob to handle async Stripe updates
• Added comprehensive test coverage for the notification flow and sync behavior

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
saas/app/models/user/notifies_account_of_email_change.rb	New concern that detects when owner email changes or ownership is transferred and notifies the account
saas/lib/fizzy/saas/engine.rb	Includes the new concern in the User model
saas/app/models/account/billing.rb	Adds method to enqueue sync job when owner email changes
saas/app/models/account/subscription.rb	Implements the Stripe customer email sync logic
saas/app/jobs/account/sync_stripe_customer_email_job.rb	Background job that calls the sync method with retry logic for Stripe errors
saas/test/models/user/notifies_account_of_email_change_test.rb	Tests for the user concern covering various scenarios
saas/test/models/account/billing_test.rb	Tests for job enqueueing behavior
saas/test/models/account/subscription_test.rb	Tests for the sync method covering edge cases

---

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[jeremy]

Re: ownership changes - addressed. The concern now handles both cases:

def account_owner_changed?
  owner? && identity && (saved_change_to_identity_id? || became_owner?)
end

def became_owner?
  saved_change_to_role? && role_before_last_save != "owner"
end

Test coverage:

• "notifies account when owner changes email"
• "notifies account when user becomes owner"
• "does not notify account when non-owner changes email"
• "does not notify account when owner becomes member"