[PM-40167] feat: Update billing domain email copy

[cyprain-okeke]

🎟️ Tracking

https://bitwarden.atlassian.net/browse/PM-40167

📔 Objective

Refreshes subject lines and body copy for nine billing-domain emails (HTML + text variants) per the PM-38898 terminology epic:

• LicenseExpired — subject only ("License expired")
• OrganizationSeatsMaxReached / OrganizationSmSeatsMaxReached / OrganizationSmServiceAccountsMaxReached — lowercased subjects; body now leads with the organization name (added OrganizationName to the view models via CoreHelpers.SanitizeForEmail)
• Provider/ProviderUpdatePaymentMethod — "Your Bitwarden organization…" copy and Admin Console navigation wording
• FamiliesForEnterprise offer (new + existing account), sponsorship reverting, and removed-from-family emails — "Sponsored Families Plan" terminology, updated subjects and body copy

Additional changes riding along:

• Removed the now-unused offerAcceptanceDate parameter from SendFamiliesForEnterpriseRemoveSponsorshipsEmailAsync (interface, both implementations, caller, tests)
• Sponsor org name in offer emails now passes through CoreHelpers.SanitizeForEmail, matching the sibling sponsorship-removal email
• Fixed the sponsorship-reverting text template referencing a nonexistent {{Date}} property (previously rendered a blank date); both variants now use {{date ExpirationDate 'MMMM dd, yyyy'}}
• Unit tests added for all changed emails, rendering the real embedded templates and asserting subjects, body copy (HTML + text), retained CTA links/disclaimers, and date formatting

Notes for reviewers:

• The ticket description still says the copy is gated behind the vfo1-foundation flag as duplicate V2 templates — that's stale. Nick Krantz confirmed the copy ships in-place with no flag; the ticket AC predates that decision.
• The removed-sponsorship email keeps the "Or click the following link: {subscription URL}" line per the ticket's copy spec. In the HTML variant this renders the raw URL as visible link text (previously anchored behind "Subscription page") and the "Or" no longer has an antecedent — flagged to product as a copy-deck question rather than deviating from the specified copy here.

[github-actions]

ℹ️ Limited Platform familiarity

This PR touches a platform-community area. The Platform team owns this code but does not actively develop it, so a Platform review here may be less authoritative than usual.

[github-actions]

🤖 Bitwarden Claude Code Review

Overall Assessment: APPROVE

Reviewed copy updates across nine billing-domain email templates (HTML + text), the OrganizationName additions to the seat/machine-account view models, subject line changes in HandlebarsMailService, and the removal of the offerAcceptanceDate parameter from SendFamiliesForEnterpriseRemoveSponsorshipsEmailAsync. Verified the signature change is propagated to both IMailService implementations and the sole caller, that all three OrganizationSeatsMaxReached*/OrganizationServiceAccountsMaxReached* view model construction sites now populate OrganizationName, and that no stale references to OfferAcceptanceDate, {{Date}}, or the old subject strings remain anywhere in the repo. Confirmed {{date ExpirationDate 'MMMM dd, yyyy'}} and {{{link SubscriptionUrl true}}} match the registered Handlebars helper signatures, and that new view model values pass through CoreHelpers.SanitizeForEmail and render via escaping stashes, consistent with sibling templates. No security, correctness, or breaking-change issues were identified.

Code Review Details

No findings at or above the reporting threshold.

Notes considered and intentionally not raised as findings:

• The dangling "Or click the following link:" line in FamiliesForEnterpriseRemovedFromFamilyUser (both variants) is already documented in the PR description as an open copy-deck question with product.
• FreeFamiliesForEnterprisePolicyEventHandler passes OrganizationSponsorship.FriendlyName into the email parameter, and SanitizeForEmail is applied to a nullable organization?.Name — both are pre-existing behaviors that this PR does not introduce or worsen.
• Removing org.ValidUntil!.Value from the handler eliminates a potential InvalidOperationException on sponsorships with a null ValidUntil; no other logic depended on it.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 63.33%. Comparing base (5358a2f) to head (e60cf96).

Additional details and impacted files

@@            Coverage Diff            @@
##           main    #8203       +/-   ##
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+ Coverage      0   63.33%   +63.33%     
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  Files         0     2381     +2381     
  Lines         0   103759   +103759     
  Branches      0     9385     +9385     
=========================================
+ Hits          0    65717    +65717     
- Misses        0    35810    +35810     
- Partials      0     2232     +2232     

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[djsmith85]

Approving for platform