Replace MailerSend template sprawl with a repo-owned render endpoint

[hturnbull93]

Summary

Replaces the 7 hand-authored MailerSend templates driven by airtable-mailersend-emails.js with a repo-owned render endpoint, matrixed on intent × chapter × language instead of one template ID per combination. Chapter content (leader, links) now comes live from the same Airtable "National Groups" data /api/national-groups already uses, instead of being hand-copied per template and drifting out of date.

• src/lib/server/onboardingEmail/ — chapter lookup, intent copy (act-now / keep-informed / volunteer / lead), language handling (en/es/fr), HTML + plain-text renderers
• src/routes/api/onboarding-email — bearer-secret POST endpoint, returns {subject, html, text}. Render-only — never sends mail itself, never touches the MailerSend API key.
• src/routes/api/unsubscribe — new. No unsubscribe mechanism existed in any of the 7 templates before this (MailerSend's unsubscribe_rate: 0 reflected "no link offered," not "no one wants out"). Flips the Members Email subscription checkbox and suppresses on both MailerSend domains.
• src/routes/onboarding-email-preview — dev-only QA page (404s outside dev), renders a sample of intent × chapter × language combos.
• airtable-mailersend-emails.js — tries the new endpoint first; on any failure (network error, timeout, non-OK response, missing fields) falls through to the original template_id logic, byte-for-byte unchanged. Worst case is today's behavior.
• email-templates/ — raw MailerSend payloads for all 7 old templates, kept as migration reference and to document routing gaps found along the way (CANADA_FR_TEMPLATE was unreachable in practice — languages is always empty at send time; Lead intent normally hands off via a mailto: link rather than a form submission, per docs/join-form-flow.md).

Please manually check / review / adjust

• Spanish copy is newly written, not adapted from anything reviewed — no es locale exists elsewhere in the codebase, and the old Spanish template only ever covered the volunteer case. Needs a native/fluent Spanish speaker from the org to read it.
• French register: the join form's French (messages.ts) uses informal tu; the old Canada-FR MailerSend template used formal vous. Matched vous to stay consistent with the reviewed body copy — meaning the email doesn't literally echo the join form's wording. Confirm that's the right call.
• Subject line no longer includes the chapter name (previously e.g. "Welcome to PauseAI UK {{first_name}}!") — check /onboarding-email-preview and confirm the new subject is acceptable.
• Visual simplification: no logo/wordmark image, social/community links render as plain text rather than icons (deliberate — avoids broken-image risk in email clients, but is a visual downgrade from the old templates). Confirm OK for v1.
• Bluesky link is hardcoded (confirmed global across every old template, including UK's — no per-chapter Bluesky field exists on NationalGroup/Airtable).
• Actually load /onboarding-email-preview locally and look at real rendered output — only agent/automated smoke-testing has happened so far, no human has eyeballed it.

Pre-merge / pre-launch checklist

• Set real values for ONBOARDING_EMAIL_RENDER_SECRET and MAILERSEND_API_KEY in prod (Netlify env vars) — both currently placeholder-only in .env (gitignored, no real values committed).
• Map the same shared secret (name it exactly Onboarding email render secret) and the optional render_endpoint_url override in the Airtable automation's script input config panel — the script references these by name but Airtable-side mapping isn't part of this repo.
• Confirm with MailerSend support whether raw (non-template_id) sends get any automatic unsubscribe-footer/compliance injection. Docs suggest that's template-engine-only, so the shell here builds its own unsubscribe link + physical address (Box C5957, Kwikstaartlaan 42, 3704GS Zeist, The Netherlands) — never got a definitive answer from MailerSend, worth chasing before this goes live.
• Trigger one real test send through the Airtable automation once deployed, to confirm the full path end-to-end (not just the isolated endpoint checks done so far).
• Once confident in the new path, consider whether/when to retire the 7 old MailerSend templates (kept live for now as the fallback).

🤖 Generated with Claude Code

https://claude.ai/code/session_01GtQwhn5Fb9eiC4LsmRs47q

[netlify]

👷 Deploy request for pauseai pending review.

Visit the deploys page to approve it

Name	Link
🔨 Latest commit	59bbca3