Add auth layer with Google/GitHub OAuth and Stripe subscription payments

[Copilot]

Adds authentication via OAuth providers and Stripe integration for monthly subscription payments to access premium content.

Authentication (NextAuth.js)

• Google and GitHub OAuth providers
• JWT session strategy with subscription status tracking
• Custom sign-in page with provider buttons
• Header component with auth status, avatar, and premium badge

Stripe Payments

• Monthly subscription checkout ($9.99/month)
• Webhook handler for subscription lifecycle events (checkout.session.completed, customer.subscription.updated/deleted, invoice.payment_failed)
• Customer portal for subscription management
• Test card numbers displayed on subscription page for development

Configuration

• .env.example template with all required variables
• Updated SETUP.md with OAuth and Stripe setup instructions
• next.config.ts updated to support API routes (static export disables auth/payments)

# Required environment variables
NEXTAUTH_SECRET=...
GOOGLE_CLIENT_ID=... / GITHUB_ID=...
STRIPE_SECRET_KEY=...
STRIPE_MONTHLY_PRICE_ID=...

Note: Subscription data uses in-memory storage for demo purposes. Replace with database for production.

Screenshots

Sign In	Subscription	Test Cards

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• https://api.github.com//advisories
  • Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node /home/REDACTED/work/_temp/ghcca-node/node/bin/node --enable-source-maps /home/REDACTED/work/_temp/copilot-developer-action-main/dist/index.js (http block)

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

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This section details on the original issue you should resolve

<issue_title>Create auth layer + connect to Stripe for payments</issue_title>
<issue_description>- Login with Google or GitHub

• Connection to Stripe to collect payment (monthly subscription to access reponses to questions)
• Make Stripe integration testable with a fake card number in test mode somehow</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Create auth layer + connect to Stripe for payments #10

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