Feat/64 social session checkout

[WilliamH141]

Description

Adds POST /api/social-sessions/:id/checkout, creates a pending registration + Stripe Checkout Session for paid social sessions. Cleans up the pending row if Stripe fails. Adds stripeCheckoutSessionId to SocialSessionRegistrations.

Closes #64

Type of change

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

• Manual testing (requires screenshots or videos)

Tested manually, see breakdown below.

Setup:

• Stripe test key in .env
• Existing paid social session (monday social session, memberPrice 14, nonMemberPrice 3)

Test 1: Happy path (guest checkout)

curl -X POST http://localhost:3000/api/social-sessions/69fef1c4e93c220e9c10e060/checkout \
  -H "Content-Type: application/json" \
  -d '{"guestName":"Test Guest","guestEmail":"guest@example.com"}'

Response: { url, registrationId: 6a1ce3547bf243fea37ba4e4 }

Stripe Checkout rendered with NZ$3.00 (non-member price) + guest@example.com pre-filled:

Payload row created with paymentStatus: pending, amountPaid: 3, stripeCheckoutSessionId populated:

Test 2: Free session rejected

Created a free session (no memberPrice / nonMemberPrice), then ran:

curl -X POST http://localhost:3000/api/social-sessions/6a1ce9397bf243fea37ba5c9/checkout \
  -H "Content-Type: application/json" \
  -d '{"guestName":"Test Guest","guestEmail":"guest@example.com"}'

Response: {"error":"This session is free — register directly without checkout."}

No new registration row created (4 rows, all for monday social session):

Test 3: Stripe failure cleans up

Temporarily set STRIPE_SECRET_KEY=sk_test_bogus in .env, restarted dev, then ran:

curl -X POST http://localhost:3000/api/social-sessions/69fef1c4e93c220e9c10e060/checkout \
  -H "Content-Type: application/json" \
  -d '{"guestName":"Test Guest 2","guestEmail":"guest2@example.com"}'

Response: {"error":"Failed to create checkout session"}

No leftover pending row for Test Guest 2, cleanup logic deleted it after Stripe failed:

Checklist before requesting a review

• My code follows the style guidelines of this project
• I have commented my code in hard-to-understand areas
• I have made corresponding changes to the documentation if needed
• I've requested a review from another team member