The "Payment due" notice the daily billing scan sends was fixed wording
baked into PaymentDueMailer. Studio admins can now view, edit and preview
its subject and body under Studio Settings -> Payment Due Email.
- PaymentDueEmailTemplate stores subject/body/item-line as us_payment_due_email_*
options, each falling back to the built-in default when blank, and renders
via {token} substitution.
- PaymentDueMailer now builds a token map from the same consolidated
items/credit/e-transfer/reference data and renders the stored template; the
default template reproduces the previous wording exactly.
- PaymentEmailController serves the view/edit/save/reset admin page
(manage_billing, nonce-checked) with a server-rendered sample preview.
- PaymentEmailPreviewEndpoint (POST us-scheduler/v1/payment-email/preview,
manage_billing) + payment-email-admin.js drive a live preview of unsaved edits.
- Submenu wired under Studio Settings; endpoint wired in RestRegistrar.
- Bump to 1.6.0 and add CHANGELOG entry. New options default gracefully, so
existing sites need no migration and send the identical notice until edited.
Co-authored-by: anthropic/claude-opus-4-8