Summary

This PR adds SMTP OAuth2 support to Joomla Global Configuration for outgoing mail, including:

• New mailer option: smtpoauth2
• OAuth2 token issue/check flow in Global Configuration
• Provider selection:
  • Microsoft
  • Google
  • Custom endpoints
• Microsoft tenant mode:
  • common endpoint
  • specific tenant ID endpoint
• SMTP XOAUTH2 token provider integration in mail factory

Why

SMTP OAuth2 is now required/strongly recommended by common providers.
This adds a core-level configuration path to use OAuth2 for SMTP without custom patches.

Main changes

• administrator/components/com_config/forms/application.xml
  • OAuth2 fields for provider/client/scope/token workflow
  • mailer option smtpoauth2
  • mailer filter fixed to allow values ending with digits
• administrator/components/com_config/src/Controller/RequestController.php
  • OAuth2 auth/callback/token-check flow
  • provider resolution and endpoint generation
• administrator/components/com_config/src/Model/ApplicationModel.php
  • config persistence and test mail updates for OAuth2
• administrator/components/com_config/src/Field/Oauth2TokenField.php
  • token UI actions in Global Config
• administrator/components/com_config/src/Helper/ConfigHelper.php
  • callback URL helper
• libraries/src/Mail/MailerFactory.php
  • smtpoauth2 transport wiring and XOAUTH2 setup
• libraries/src/Mail/SmtpOAuth2TokenProvider.php
  • refresh-token based access token retrieval
• administrator/language/en-GB/com_config.ini
  • new labels/messages

Notes

• Microsoft single-tenant apps are supported through tenant-specific endpoint generation.

Testing performed

• Config save with smtpoauth2
• OAuth2 token issuance and storage
• Token validity check
• SMTP test mail with Microsoft tenant-specific endpoint