feat(auth): hide/show GitHub & Google login (#384)

[grootbro]

Summary

• Social login buttons render only when the matching OAuth credentials are set (CLIENT_ID + SECRET + REDIRECT_URI)
• Optional DISABLE_GITHUB_AUTH / DISABLE_GOOGLE_AUTH to hide login while keeping Google creds for Search Console
• auth.getOAuthProviders + server-side gate on signInOAuth
• Docs: self-hosting guide + environment variables for GitHub/Google setup

Fixes #384

Test plan

• Self-host without OAuth env → login/onboarding show email only (no Or divider)
• Set GitHub credentials only → GitHub button appears; Google hidden
• Set DISABLE_GOOGLE_AUTH=true with Google creds → Google button hidden
• Cloud (both providers configured) → both buttons still show
• signInOAuth for a disabled provider returns a bad-request error
• CI: oauth-providers unit tests pass

Made with Cursor

Summary by CodeRabbit

• New Features

  • Added support for configurable GitHub and Google social login on self-hosted installations.
  • Login and onboarding screens now display social sign-in options only when providers are fully configured and enabled.
  • Added validation to prevent sign-in attempts through disabled providers.

• Documentation

  • Added setup instructions and environment variable references for configuring or hiding GitHub and Google sign-in.
  • Clarified that email/password login remains available without additional social login setup.

• Tests

  • Added coverage for provider credential requirements, disable flags, and provider availability.

[coderabbitai]

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ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: 7b8d5304-fb2f-4df0-944b-eba0fca92af0

📥 Commits

Reviewing files that changed from the base of the PR and between 3060ca1 and 26a1e6b.

📒 Files selected for processing (9)

• apps/public/content/docs/self-hosting/environment-variables.mdx
• apps/public/content/docs/self-hosting/self-hosting.mdx
• apps/start/src/hooks/use-oauth-providers.ts
• apps/start/src/routes/_login.login.tsx
• apps/start/src/routes/_public.onboarding.tsx
• packages/auth/src/index.ts
• packages/auth/src/oauth-providers.test.ts
• packages/auth/src/oauth-providers.ts
• packages/trpc/src/routers/auth.ts

Included review availability: Your plan provides up to 8 included reviews per hour; 5 remain after this review.

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📝 Walkthrough

Walkthrough

The change adds GitHub and Google OAuth configuration helpers, exposes provider availability through tRPC, blocks disabled sign-in attempts, conditionally renders login and onboarding controls, adds tests, and documents self-hosted OAuth setup.

Changes

OAuth provider availability

Layer / File(s)	Summary
Provider configuration and validation packages/auth/src/oauth-providers.ts, packages/auth/src/oauth-providers.test.ts, packages/auth/src/index.ts	The auth package detects configured providers, applies disable flags, exports availability helpers, and tests credential and flag handling.
Auth provider API and sign-in guard packages/trpc/src/routers/auth.ts	The auth router exposes enabled providers, accepts only GitHub and Google for OAuth sign-in, and rejects disabled providers.
Conditional login and onboarding UI apps/start/src/hooks/use-oauth-providers.ts, apps/start/src/routes/_login.login.tsx, apps/start/src/routes/_public.onboarding.tsx	The login and onboarding routes preload provider availability and render OAuth controls only for enabled providers.
Self-hosting OAuth documentation apps/public/content/docs/self-hosting/environment-variables.mdx, apps/public/content/docs/self-hosting/self-hosting.mdx	The documentation describes OAuth variables, setup steps, redirect URIs, and disable flags.

Estimated code review effort: 3 (Moderate) | ~25 minutes

Merge Risk: ⚪ Minimal · up to 26a1e

GitHub and Google login buttons now reflect configured credentials and disable flags, while disabled providers are rejected server-side and email authentication remains available. No concrete merge-blocking risk remains.

Sequence Diagram(s)

sequenceDiagram
  participant LoginPage
  participant AuthRouter
  participant AuthConfig
  participant Environment
  LoginPage->>AuthRouter: request OAuth provider availability
  AuthRouter->>AuthConfig: evaluate enabled providers
  AuthConfig->>Environment: read credentials and disable flags
  Environment-->>AuthConfig: return configuration
  AuthConfig-->>AuthRouter: return provider states
  AuthRouter-->>LoginPage: return enabled providers

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Suggested reviewers: lindesvard

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 30.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 7 files. (2 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: configurable visibility for GitHub and Google authentication providers.
Linked Issues check	✅ Passed	The changes satisfy issue #384 by adding provider visibility controls, conditional login buttons, server-side provider validation, and documentation for GitHub and Google OAuth configuration.
Out of Scope Changes check	✅ Passed	The code, tests, documentation, and API changes are directly related to configurable GitHub and Google authentication providers and the requirements in issue #384.

Full details: Docstring Coverage

Explanation

Docstring coverage is 30.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 10 functions across 7 files. (2 skipped: 2 unsupported.)

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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