Jenkins email notifications using Outlook SMTP with OAuth

This project adds OAuth 2.0 support to the Jenkins email-ext plugin, addressing the deprecation of basic SMTP authentication by providers like Microsoft and Google. It integrates with the oauth-credentials framework to securely obtain access tokens and enables XOAUTH2-based SMTP authentication using Jakarta Mail. The solution is provider-agnostic, allowing compatibility with multiple email services. Deliverables include OAuth integration, UI updates for configuration and credential selection, a test email feature, comprehensive test coverage, and full documentation, while maintaining backward compatibility with existing authentication methods.