Bug: Handle GitHub OAuth Access Denied Error

When using GitHub OAuth for authentication in our application, users may encounter an "access_denied" error if they deny our application access, leading to dead blank screen (see screenshot). This error needs to be handled gracefully to provide a good user experience and guide users on how to resolve the issue.

Solution:

1. Error Detection: Implement error detection logic in the OAuth callback handler to identify the "access_denied" error.

2. Error Handling: When the "access_denied" error is detected, display a user-friendly message to inform the user that their access has been denied and provide guidance on how to proceed.

3. Logging: Log the error details for debugging and monitoring purposes.

4. Redirect: Optionally, provide a redirect mechanism to allow the user to retry the authentication process or navigate back to a previous page.

Example Error Details:

• Full URL: http://localhost:4321/api/github/oauth/callback?error=access_denied&error_description=The+user+has+denied+your+application+access.&error_uri=https%3A%2F%2Fdocs.github.com%2Fapps%2Fmanaging-oauth-apps%2Ftroubleshooting-authorization-request-errors%2F%23access-denied&state=path%3A%2Fsandbox%7Credirect%3Atrue
• Error: access_denied
• Description: The user has denied your application access.
• Error URI: GitHub OAuth Troubleshooting Documentation
• State: path:/sandbox|redirect:true

Acceptance Criteria:

• Users are presented with a clear message when the "access_denied" error occurs.
• The message includes instructions or a link to resolve the issue.

Related Tasks:

• Implement error detection in the OAuth callback handler.
• Design and implement a user-friendly error message for the "access_denied" error.
• Test the error handling mechanism to ensure it works as expected.

Additional Notes:

• This issue is crucial for maintaining a positive user experience and ensuring users can easily resolve authentication issues.

Comienza en el controlador de callback de GitHub OAuth en /api/github/oauth/callback y reproduce la URL access_denied mostrada en el issue. Traza cómo responde actualmente el callback y, a continuación, verifica que la denegación produzca un mensaje claro con orientación para resolverla y que los detalles del error se registren; prueba el comportamiento de reintento o navegación si está implementado.