- Add ValidateSession gRPC method for proxy-side user validation
- Move group access validation from REST callback to gRPC layer
- Capture user info in access logs via CapturedData mutable pointer
- Create validate_session_test.go for gRPC validation tests
- Simplify auth_callback_integration_test.go to create accounts
programmatically instead of using SQL file
- SQL test data file now only used by validate_session_test.go
