Self-service security alert handling with GitLab's UAM

Introduced the User Attestation Module (UAM) as a Slack-first automation to streamline security alert handling. UAM allows team members to directly attest to the legitimacy of security alerts, reducing alert fatigue for the Security Incident Response Team (SIRT) and creating a new tier of alert handling. It integrates with GitLab API, Slack API, Tines, Devo, and a Metrics DB to manage the workflow, collect evidence, and provide audit trails and metrics.