Manage CI/CD credentials with GitLab Secrets Manager

What this post added

This post introduces GitLab Secrets Manager, a new capability for managing CI/CD credentials. It details how secrets are declared in `.gitlab-ci.yml` using the `secrets:` keyword and scoped to specific jobs based on environment and branch attributes. It highlights the use of OpenBao as the underlying technology and emphasizes the integration with existing GitLab access control models for enhanced security and reduced operational overhead compared to standalone vault solutions. The post also outlines the audit logging capabilities for secret reads and management operations.