feat: add support for Dynamic App Base URL

[frederikprijck]

Summary

Adds dynamic application base URL support to @auth0/auth0-nuxt, allowing a single Nuxt app to serve multiple origins from one Auth0 application.

appBaseUrl now supports three modes:

• Static ("https://app.example.com") — unchanged current behavior.
• Allow-list (["https://a.com", "https://b.com"], or comma-separated via NUXT_AUTH0_APP_BASE_URL) — the request origin is matched against the list. Recommended for production.
• Dynamic (omitted) — the base URL is inferred per request from the host, honoring x-forwarded-host / x-forwarded-proto.

Changes

• New runtime/server/utils/app-base-url.ts — isUrl, inferBaseUrlFromRequest, resolveAppBaseUrl (uses h3's getRequestHost/getRequestProtocol).
• New runtime/server/utils/config.ts — parseAppBaseUrl, validateAppBaseUrl, enforceSecureCookies, resolveAuth0Options. Comma-separated parsing, validation, and production secure-cookie enforcement. Returns a new options object (the Nuxt runtime config is frozen).
• Plugin auth.server.ts — resolves/validates options; the hard appBaseUrl required-check is removed (dynamic mode omits it).
• use-auth0.ts — only bakes a static redirect_uri; in dynamic/allow-list mode the login handler supplies it per request.
• Handlers — login/callback/logout resolve the base URL from their own event.
• Types — appBaseUrl?: string | string[]; InvalidConfigurationError re-exported from the module entry.
• Example — new examples/example-nuxt-web-dynamic-app-base-url (two-host allow-list demo).
• Docs — README + EXAMPLES document the three modes and the production secure-cookie requirement.

Design spec and implementation plan are included under docs/superpowers/.

Test Plan

• Unit tests pass (npm run test:unit — 76 passing, +32 new across resolver, config, and the three handlers)
• Lint clean (npm run lint)
• Build succeeds (npm run build), InvalidConfigurationError exported
• E2E (npm run test:e2e) — runs in CI with Auth0 tenant secrets (live login flow); not runnable locally without credentials

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: f63902fa-0177-4b8f-b6a5-9f7e2896fe92

📥 Commits

Reviewing files that changed from the base of the PR and between 7931c04 and 4b2f9c5.

⛔ Files ignored due to path filters (2)

• examples/example-nuxt-web-dynamic-app-base-url/public/favicon.ico is excluded by !**/*.ico
• examples/example-nuxt-web-dynamic-app-base-url/public/img/auth0.png is excluded by !**/*.png

📒 Files selected for processing (28)

• examples/example-nuxt-web-dynamic-app-base-url/.env.example
• examples/example-nuxt-web-dynamic-app-base-url/.gitignore
• examples/example-nuxt-web-dynamic-app-base-url/README.md
• examples/example-nuxt-web-dynamic-app-base-url/app.vue
• examples/example-nuxt-web-dynamic-app-base-url/nuxt.config.ts
• examples/example-nuxt-web-dynamic-app-base-url/package.json
• examples/example-nuxt-web-dynamic-app-base-url/pages/index.vue
• examples/example-nuxt-web-dynamic-app-base-url/pages/private.vue
• examples/example-nuxt-web-dynamic-app-base-url/pages/public.vue
• examples/example-nuxt-web-dynamic-app-base-url/public/robots.txt
• examples/example-nuxt-web-dynamic-app-base-url/server/middleware/auth.server.ts
• examples/example-nuxt-web-dynamic-app-base-url/tsconfig.json
• packages/auth0-nuxt/EXAMPLES.md
• packages/auth0-nuxt/README.md
• packages/auth0-nuxt/src/module.ts
• packages/auth0-nuxt/src/runtime/server/api/auth/callback.get.spec.ts
• packages/auth0-nuxt/src/runtime/server/api/auth/callback.get.ts
• packages/auth0-nuxt/src/runtime/server/api/auth/login.get.spec.ts
• packages/auth0-nuxt/src/runtime/server/api/auth/login.get.ts
• packages/auth0-nuxt/src/runtime/server/api/auth/logout.get.spec.ts
• packages/auth0-nuxt/src/runtime/server/api/auth/logout.get.ts
• packages/auth0-nuxt/src/runtime/server/composables/use-auth0.ts
• packages/auth0-nuxt/src/runtime/server/plugins/auth.server.ts
• packages/auth0-nuxt/src/runtime/server/utils/app-base-url.spec.ts
• packages/auth0-nuxt/src/runtime/server/utils/app-base-url.ts
• packages/auth0-nuxt/src/runtime/server/utils/config.spec.ts
• packages/auth0-nuxt/src/runtime/server/utils/config.ts
• packages/auth0-nuxt/src/types.ts

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/dynamic-app-base-url

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