📧 feat: Mailgun API Email Configuration

[danny-avila]

Relevant documentation: LibreChat-AI/librechat.ai#317

Summary

• Integrated Mailgun API support as an alternative to SMTP for email sending with proper configuration detection and fallback handling
• Enhanced email configuration validation to support both Mailgun and SMTP providers
• Improved error handling and logging throughout authentication flows

Other Changes

• Fixed edge case in deleteUserController where deletion would fail when users had no conversations
• Added undefined password validation in local authentication strategy to prevent crashes when users registered via social/OIDC login attempt password authentication
• Fixed undefined SESSION_EXPIRY environment variable handling in user token generation to prevent crashes when the variable is not set or contains invalid expressions
• Added comprehensive test suite for the generateToken method with 163 lines of test coverage including edge cases for invalid SESSION_EXPIRY values
  • [Bug]: Login broken after SESSION_EXPIRY change #7731

Change Type

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)

Testing

I tested the authentication flows with various SESSION_EXPIRY configurations and verified the email functionality works with both Mailgun and SMTP providers. The new test suite covers all edge cases for token generation including invalid expressions and missing environment variables.

Test Configuration:

• Jest test environment with MongoDB mocking
• Various SESSION_EXPIRY values including empty strings, invalid expressions, and valid time expressions
• Authentication testing with users who have no password set
• Email provider testing with both Mailgun and SMTP configurations

Checklist

• My code adheres to this project's style guidelines
• I have performed a self-review of my own code
• I have commented in any complex areas of my code
• I have made pertinent documentation changes
• My changes do not introduce new warnings
• I have written tests demonstrating that my changes are effective or that my feature works
• Local unit tests pass with my changes
• Any changes dependent on mine have been merged and published in downstream modules.