Fix: Default error_scenario.enabled to true when configured

[Copilot]

External tests failed to trigger OAuth error scenarios because the enabled field defaulted to false and wasn't documented. Users configured error scenarios without knowing to set "enabled": true, causing scenarios to be stored but never activated.

Changes

Config Handler (internal/handlers/config.go)

• Changed ErrorScenario.Enabled from bool to *bool to distinguish unset (nil) from explicit false
• Default to true when nil, allowing {"endpoint": "authorize", "error": "unauthorized_client"} to work immediately

Documentation (README.md)

• Added complete list of supported OAuth2 error codes per endpoint (authorize, token, userinfo)
• Clarified enabled field is optional and defaults to true

Tests (internal/handlers/config_test.go)

• Added coverage for default-enabled behavior and explicit disable

Example

Before (broken):

{
  "error_scenario": {
    "endpoint": "authorize",
    "error": "unauthorized_client"
  }
}

Error stored but never triggers (enabled defaults to false).

After (fixed):

{
  "error_scenario": {
    "endpoint": "authorize", 
    "error": "unauthorized_client"
  }
}

Works immediately. Set "enabled": false to explicitly disable.

Impact

Fixes all 5 previously-failing error scenarios: unauthorized_client, invalid_scope, temporarily_unavailable, invalid_request, unsupported_response_type. Backward compatible with existing configs.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[FEATURE] extend error scenarios</issue_title>
<issue_description>## Summary

After re-running the previously skipped OAuth error scenario tests, we discovered that the mock OAuth server has been partially updated and now supports some error scenarios!

Test Results

✅ Tests Now Passing (10 total)

Basic OAuth Flow (7 tests):

1. ✅ should complete OAuth flow with mock server
2. ✅ should receive session cookie after authentication
3. ✅ should show user information on dashboard
4. ✅ should be able to logout
5. ✅ should redirect to dashboard after login
6. ✅ Basic Page Navigation: should load home page
7. ✅ Basic Page Navigation: should have navigation links on home page

OAuth Error Scenarios (3 tests - NOW WORKING!):
8. ✅ should handle OAuth access denied error ⭐ NEW
9. ✅ should handle server error from OAuth provider ⭐ NEW
10. ✅ should handle token endpoint error ⭐ NEW

⏭️ Tests Still Skipped (7 total)

Requires mock OAuth server improvements:

1. ⏭️ should redirect to login when accessing dashboard without authentication

   • Issue: Navigating to /dashboard without auth still completes OAuth flow
   • Needs: Proper unauthenticated redirect handling

2. ⏭️ should handle unauthorized client error

   • Issue: Error scenario not properly blocking authentication

3. ⏭️ should handle invalid scope error

   • Issue: Error scenario not properly blocking authentication

4. ⏭️ should handle temporarily unavailable error

   • Issue: Error scenario not properly blocking authentication

5. ⏭️ should handle invalid request error

   • Issue: Error scenario not properly blocking authentication

6. ⏭️ should handle unsupported response type error

   • Issue: Error scenario not properly blocking authentication

7. ⏭️ should recover from error scenario when disabled

   • Issue: Depends on other error scenarios working first

Mock OAuth Server Status

Current Version:

• Created: October 25, 2025
• Digest: sha256:cafa3d8522d5f3147956b1bcaecaeb35493ac93ebde7674ec8b8d1be960fb6f0
• Repository: https://github.com/chrisw-dev/golang-mock-oauth2-server

Error Scenarios - Support Status:

Error Type	Status	Notes
access_denied	✅ WORKS	Properly blocks auth and redirects
server_error	✅ WORKS	Properly handled
Token endpoint errors	✅ WORKS	invalid_grant working
unauthorized_client	❌ FAILS	Still auto-approves
invalid_scope	❌ FAILS	Still auto-approves
temporarily_unavailable	❌ FAILS	Still auto-approves
invalid_request	❌ FAILS	Still auto-approves
unsupported_response_type	❌ FAILS	Still auto-approves

Progress

Before (original issue):

• 9 tests failing
• 1 test skipped
• 7 tests passing

After mock OAuth update:

• 0 tests failing ✨
• 7 tests skipped (waiting on mock OAuth improvements)
• 10 tests passing ✅ (+3 new passing tests!)
  </issue_description>

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

• Fixes [FEATURE] extend error scenarios #13

---

💡 You can make Copilot smarter by setting up custom instructions, customizing its development environment and configuring Model Context Protocol (MCP) servers. Learn more Copilot coding agent tips in the docs.