Oauth - GitHub Login Screen Integration

[coderabbitai]

Problem

The login screen does not initiate the GitHub flow or complete the exchange after deep-link callback.

Scope

• Add GitHub button to initiate authorize().
• On deep link, validate state and call OAuthService.signInWithOAuth with provider GITHUB.

Approach

Use DeepLinkHandler.listen to receive code/state and finalize the login.

Dependencies

• Blocked By:
• Blocks:

Files to Modify/Create

• talawa/lib/views/auth/login_screen.dart
• talawa/lib/services/oauth/deep_link_handler.dart

Acceptance Criteria

• All existing functionality must be maintained
• Implementation must ensure no breaking changes when PR is merged

Testing Requirements

• All tests must pass successfully
• Code coverage must be >= 96%

Sample Code

This sample code is only representative of what could be done. It is provided only to give a general outline. You will need to use your initiative and industry best practices to find a solution that is suitable for the application.

// talawa/lib/views/auth/login_screen.dart (snippet for deep link completion)
_streamSub ??= deepLinkHandler.listen((code, state) async {
  // optional: verify state from SharedPreferences
  await oauthService.signInWithOAuth(
    provider: "GITHUB", authorizationCode: code, redirectUri: "talawa://oauth/callback");
});