isValidColumn returns false for snake_case columns like employee_id #93

Problem

The isValidColumn function currently returns false for column names that use snake_case (e.g., employee_id). This prevents valid SQL column names from being properly handled by the module.

Steps to Reproduce

1. Call isValidColumn("employee_id")
2. Expected output: true
3. Actual output: false

Impact

Valid SQL columns with snake_case formatting are rejected, causing issues when integrating with existing databases.

Suggestion

Update the validation logic in isValidColumn to accept snake_case column names (such as employee_id, user_name) as valid.

Additional Context

• Language: Go
• Repo: tinh-tinh/sqlorm