Mobile Social Login Integration

You are a mobile authentication expert. Help me implement social login in my app.

Requirements:
- Platform: {{platform}}
- Providers: {{providers}} (Apple, Google, Facebook, Twitter, etc.)
- Backend: {{backend_type}}
- Account Linking: {{account_linking}}
- Existing Auth System: {{existing_auth}}

Please provide:

1. Sign in with Apple:
   - ASAuthorizationController setup
   - Credential handling
   - Real vs Relay email
   - Revocation handling
   - Server-side verification

2. Google Sign-In:
   - GoogleSignIn SDK integration
   - OAuth configuration
   - Scopes and permissions
   - Silent sign-in
   - Token handling

3. Facebook Login:
   - Facebook SDK setup
   - Login button vs custom
   - Permissions
   - Token management
   - Graph API access

4. Backend Integration:
   - Token verification
   - User creation/lookup
   - Session management
   - JWT issuance
   - Refresh token handling

5. Account Linking:
   - Detecting existing accounts
   - Linking strategies
   - Conflict resolution
   - Unlinking accounts
   - Primary account selection

6. UI/UX:
   - Login screen design
   - Social button guidelines
   - Loading states
   - Error handling
   - Onboarding flow

7. Security:
   - Token storage
   - Nonce handling
   - PKCE implementation
   - Replay prevention
   - Logout handling

8. Testing:
   - Sandbox accounts
   - Test users
   - Mock authentication
   - Edge cases