[PM-37514] Support Teams 2019 Migration

[sbrown-livefront]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-37514

📔 Objective

Adds the Teams 2019 → Teams Current pricing-migration paths (Monthly and Annual) to the deferred
price-increase migration engine (epic PM-37496).

"Teams 2019 Packaged" is a flat base covering 5 included seats, plus a per-seat overage for seats beyond 5. Current Teams is pure per-seat.

• Orgs with < 5 occupied seats are billed for actual occupied seats — unused base headroom
  disappears.
• Orgs with ≥ 5 keep their current purchased seat count.

Unlike Teams Starter (a flat bundle), Teams 2019 carries a per-seat overage line, so
HasNonSeatBasedPasswordManagerPlan() is false for it — that distinction drives most of the
changes below.

Code changes

• Paths & policy — registers Teams2019AnnualToCurrent / Teams2019MonthlyToCurrent
  (append-only MigrationPathIds 9, 10; 7–8 reserved for the in-flight Teams Starter paths). Adds
  SeatCountPolicy { Preserve, ActualUsage } to MigrationPath; Teams 2019 uses ActualUsage, all
  other paths default to Preserve.
• Price mapping (OrganizationPlanMigrationPriceMapper) — a guarded Packaged → Scalable case
  maps the flat base price (StripePlanId) to the target per-seat price; the not-null guard keeps a
  null == null misfire off Scalable sources.
• Phase 2 schedule (PriceIncreaseScheduler) — for ActualUsage, the base line and the
  seat-overage line (both map to the same target seat price) collapse into a single seat line
  billed at occupied < base ? occupied : purchased, floored at 1. Storage and other items pass
  through unchanged.
• Renewal email (UpcomingInvoiceHandler) — reuses BusinessPlanRenewal2020MigrationMail; the
  quoted seat count matches what Phase 2 bills (occupied for < 5, purchased for ≥ 5).
• Renewal activation (SubscriptionUpdatedHandler) — source detection now identifies packaged
  sources by their base price (so a sub-5 Teams 2019 org, which has no overage line, is still
  recognized when the schedule advances), and the organization.Seats reconciliation (PM-39562,
  [PM-39562] fix: Reconcile org seats to billed quantity on packaged-plan migration #7869) now also fires for Teams 2019 — reconciling Seats to the billed quantity.

Notes for reviewers

• MaxAutoscaleSeats is preserved by construction — ChangePlan doesn't touch it and the
  reconciliation writes only Seats.

📸 Screenshots

Incoming

[codecov]

Codecov Report

❌ Patch coverage is 92.75362% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 61.22%. Comparing base (0ec0b23) to head (4d8a784).
⚠️ Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
...Services/Implementations/UpcomingInvoiceHandler.cs	80.00%	0 Missing and 3 partials ⚠️
...ices/Implementations/SubscriptionUpdatedHandler.cs	88.88%	0 Missing and 1 partial ⚠️
src/Core/Billing/Pricing/PriceIncreaseScheduler.cs	96.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7864      +/-   ##
==========================================
+ Coverage   61.21%   61.22%   +0.01%     
==========================================
  Files        2217     2219       +2     
  Lines       98051    98098      +47     
  Branches     8849     8853       +4     
==========================================
+ Hits        60023    60065      +42     
- Misses      35911    35916       +5     
  Partials     2117     2117              

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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
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

Reviewed the Teams 2019 → Teams Current migration paths added to the deferred price-increase engine. Examined the new SeatCountPolicy value object, the scheduler's Packaged-source seat collapsing (PriceIncreaseScheduler.CalculateTargetPlanSeatCountAsync), the renewal-email seat resolution (UpcomingInvoiceHandler.ResolveSeatCountAsync), and the renewal-activation seat reconciliation (SubscriptionUpdatedHandler). The three billed-quantity touchpoints (scheduler, email, reconciliation) resolve seats consistently (occupied < base ? occupied : purchased) and the append-only MigrationPathId snapshot guard is updated correctly.

Code Review Details

No blocking findings. The change is well-scoped and backed by thorough unit tests covering the seat-resolution boundaries (below base, at base, above base, purchased > occupied), storage line-item preservation, sub-5 source detection by base price, and the snapshot/registry immutability guards.