example: marketing waitlist signup (public form → PostKitClient)

[patoperpetua]

Parent: #7

Goal

Add a minimal, testable waitlist/whitelist signup example so epic #7 scenario 3 is covered and the epic can close.

Scope

• New private package examples/marketing-waitlist/ mirroring examples/marketing-contact-us/
• Framework-agnostic handler: validate email (+ optional name), send confirmation to the submitted address with a server-owned template key (e.g. marketing.waitlist-confirm)
• Optional internal notify send is out of scope unless trivial; prefer one confirmation template
• Seed content/email-templates/marketing.waitlist-confirm/
• Specs with mocked PostKitClient fetch (no network)
• README + link from docs/guides/public-forms.md
• Comment on Epic: Add tenant onboarding, examples, and end-to-end documentation #7 and close the epic when this merges (or open a follow-up close comment)

Acceptance criteria

• pnpm --filter @singleton-sd/example-marketing-waitlist test passes
• Handler ignores caller-supplied template / to / from / subject except using validated email as to
• Extra controls documented: rate-limit per address, one send per submission, dedicated template (rate limiter itself may be stubbed/documented, not implemented in the example)
• Epic Epic: Add tenant onboarding, examples, and end-to-end documentation #7 scenario 3 demonstrably covered

Out of scope

• Captcha / production rate limiter implementation
• InkAds product wiring (separate repo issues)
• Admin editor / Decap work

Depends on

None (Contact Us example already merged).

[patoperpetua]

PR: #137