Draft: Adding application code

This merge request sets up a complete CI/CD pipeline for a Java Spring Boot application. It adds configuration files to ignore build artifacts and temporary files, creates an automated pipeline that builds the application, runs security scans, creates Docker images, and deploys the app to Google Cloud Platform. The pipeline includes automatic deployment of temporary review environments for testing merge requests, as well as production deployment when code is merged to the main branch. It also includes Maven wrapper scripts for consistent build environments and Docker configuration to package the application for deployment.