Support audit log

[flpanbin]

Summary

This PR introduces an audit logging feature to ttyd, allowing the recording of user input commands for security and compliance purposes. The following new command-line options are added:

• --audit-enable: Enable command audit logging.
• --audit-log-file <path>: Specify the audit log file path (default: /var/log/ttyd/audit.log).
• --audit-field <key=value>: Add custom fields to each audit log entry. This option can be used multiple times to include additional metadata.

Features

• Audit Logging: When enabled, ttyd records all user input commands to the specified log file.
• Custom Fields: Users can add custom key-value fields to each log entry for enhanced traceability.
• Log Rotation: The audit log supports automatic rotation based on file size (default size is 10MB), ensuring logs do not grow indefinitely.

Usage:

ttyd --audit-enable --audit-log-file /var/log/ttyd/audit-tmp.log --audit-field=cluster=cluster1 --audit-field=namespace=ns3 --audit-field=username=user1