[PM-34866][PM-34865] Fix EnableAutomaticTaxAsync to update schedule phases

[connerbw]

🎟️ Tracking

• https://bitwarden.atlassian.net/browse/PM-34866
• https://bitwarden.atlassian.net/browse/PM-34865

📔 Objective

Fixes two defects in EnableAutomaticTaxAsync (in both UpcomingInvoiceHandler and UpdateBillingAddressCommand):

PM-34866: Tax remains disabled when automatic tax is set to false during Phase 1. The method only updated DefaultSettings.AutomaticTax on the schedule, which does not propagate to the active phase or the underlying subscription.

PM-34865: One-time migration discount (milestone-3/milestone-2c) incorrectly reapplied on invoice.upcoming when tax is disabled during Phase 1.

Fix

Updates EnableAutomaticTaxAsync to echo all schedule phases with AutomaticTax.Enabled = true set on each phase — matching the pattern used by every other schedule-aware method in the codebase (SubscriberService.CancelSubscription, UpdatePremiumStorageCommand, ReinstateSubscriptionCommand, etc.).

Key details:

• Completed phases are skipped (Stripe rejects updates to past phases)
• One-time migration discounts on already-active phases are cleared to prevent Stripe from reapplying consumed coupons (same pattern as UpdatePremiumStorageCommand)
• Phase items, dates, and proration behavior are preserved unchanged
• Test clock FrozenTime is used for phase filtering to ensure correct behavior during QA testing with Stripe test clocks

📸 Screenshots

N/A — no UI changes.

[github-actions]

Bitwarden Claude Code Review

Overall Assessment: APPROVE

This PR fixes EnableAutomaticTaxAsync in both UpcomingInvoiceHandler and UpdateBillingAddressCommand to echo subscription schedule phases with AutomaticTax.Enabled = true on each phase, rather than only updating DefaultSettings. The implementation correctly follows the established schedule-aware pattern used by UpdatePremiumStorageCommand and other billing commands. The Stripe API Expand lists are updated to include subscriptions.data.test_clock so that FrozenTime is available for phase filtering. Test coverage is thorough, validating the two-phase case, the completed-phase skip with consumed-discount clearing, and the no-schedule fallback path.

Code Review Details

No findings. The phase filtering logic, discount consumption handling, test clock support, and item/date preservation are all consistent with existing codebase patterns. The previous review finding about using subscription.TestClock?.FrozenTime instead of bare DateTime.UtcNow has been addressed in both files.

[github-actions]

Checkmarx One – Scan Summary & Details – 2186b374-4df3-4e23-ba80-6e4ab95a9648

Great job! No new security vulnerabilities introduced in this pull request

[codecov]

Codecov Report

❌ Patch coverage is 89.85507% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 58.48%. Comparing base (52ff4a7) to head (9331a7b).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ng/Payment/Commands/UpdateBillingAddressCommand.cs	85.71%	2 Missing and 3 partials ⚠️
...Services/Implementations/UpcomingInvoiceHandler.cs	94.11%	0 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7437      +/-   ##
==========================================
+ Coverage   58.46%   58.48%   +0.02%     
==========================================
  Files        2066     2066              
  Lines       91071    91135      +64     
  Branches     8100     8110      +10     
==========================================
+ Hits        53247    53303      +56     
- Misses      35922    35925       +3     
- Partials     1902     1907       +5     

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[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
29.6% Duplication on New Code

See analysis details on SonarQube Cloud